The effect of progressive muscle relaxation in the basal cortisol response of high and low neurocitism students

DOCTORAL THESIS 2014

THE EFFECT OF PROGRESSIVE MUSCLE

RELAXATION IN THE BASAL CORTISOL RESPONSE OF HIGH AND LOW NEUROTICISM STUDENTS

Karin Chellew Gâlvez

Universität de les Ules Balears

DOCTORAL THESIS 2014

Doctoral Programme of Cognition and Human Evolution

THE EFFECT OF PROGRESSIVE MUSCLE

RELAXATION IN THE BASAL CORTISOL RESPONSE OF HIGH AND LOW NEUROTICISM STUDENTS

Karin Chellew Gâlvez

Director: Gloria Garcia de la Banda Co-director: Phil Evans

Ponent: Enric Munar Roca

Doctor by the Universitat de les Illes Balears

To my parents, Tito and Lily

and to my godparents, Olivia and Roberto

"We have negative mental habits that come up over and over again.

One of the most significant negative habits we should be aware of is that of constantly allowing our mind to run off into the future. Perhaps we got this from our parents. Carried away by our worries, we're unable to live fully and happily in the present. Deep down, we believe we can't really be happy just yet—that we still have a few more boxes to be checked off before we can really enjoy life.

We speculate, dream, strategize, and plan for these "conditions of happiness"

we want to have in the future; and we continually chase after that future, even while we sleep. We may have fears about the future because we don't know how it's going to turn out and these worries and anxieties keep us from enjoying

being here now."

Thich Nhat Hanh Peace is every breath: A practice for our busy lives (2012, p. 23)

Acknowledgements

Infinitive thanks:

T o m y w h o l e family w h o is always there to support m e a n d gives m e the w i n g s to p u r s u e m y goals a n d help m e to carry on all t h e s e y e a r s . I k n o w that it has not always b e e n easy. T o my girls, Vicky, M a l e n , Julia F. C., Natalia, Julia U., a n d E m n i t a , for always being there w h e n I n e e d e d it the m o s t ! T o m y very g o o d friends from IFISC, specially to: Pedrito, Enrico, Miguel, a n d P r z e m e k for all t h o s e great times that w e s h a r e d this last two years at lunch, rutas martianas, "fiestas multiculturales", outings, paintballs, etc., that gave m e the strength a n d motivated m e to carry o n . G u y s , Y O U R O C K ! T o María S a l e t a s w h o always w a s there to help me.

T o Diego, w h o always m a d e m e laugh a n d m a d e m y day a little bit less stressful at the bar. T o m y colleagues, g o o d friends, a n d m y s e c o n d family: Vicky, J a c o b o , P e p , Malen, a n d S e l e n e for all t h e s e years of hard w o r k at the office, travels, breakfasts, etc. G u y s y o u are the best, thank y o u for all the g o o d experiences! T o Esperanga, t h a n k y o u for all t h o s e m o m e n t s that w e shared, at breakfast, travelling by car, conversations, etc., they w e r e very special to me. T o all the extraordinary people a n d professors that I had the pleasure to m e e t in so m a n y places all t h e s e years, t h a n k y o u for all that I learned from y o u ! T o y o u Przemek, y o u have m a d e m y last years a very special time. T o Phil Evans, t h a n k y o u to be part of this process a n d t h a n k y o u to share all your k n o w l e d g e a n d time with me. Finally, to Gloria, since the m o m e n t I met y o u , y o u have b e e n an inspiration a n d a role model for m e . I have no w o r d s to express m y gratitude to y o u for always being there for me, to s h a r e all your k n o w l e d g e , time a n d dedication.

Agradecimientos

Gracias infinitas:

A t o d a mi familia que s i e m p r e está allí para a p o y a r m e y d a r m e las alas para perseguir mis objetivos y a y u d a r m e a continuar durante todos estos años. Sé que no s i e m p r e ha sido fácil. A mis chicas: Vicky, M a l e n , Julia F. C., Natalia, Julia U. y Emnita por estar s i e m p r e allí c u a n d o m á s las he necesitado. A mis m u y b u e n o s a m i g o s del IFISC, e s p e c i a l m e n t e a: Pedrito, Enrico, Miguel y P r z e m e k por todos e s o s b u e n o s m o m e n t o s que h e m o s compartido estos últimos años en las comidas, rutas martianas, fiestas multiculturales, excursiones, paintballs, etc., que m e han d a d o la fuerza y m e han motivado a seguir. Chicos, Y O U R O C K ! A María Saletas, quien s i e m p r e ha estado allí para a y u d a r m e . A Diego, que s i e m p r e m e hizo reír y hacer mi día un poco m e n o s estresante en el bar. A mis colegas, b u e n o s a m i g o s y mi s e g u n d a familia: Vicky, J a c o b o , Pep, Malen y Selene por todos estos a ñ o s de arduo trabajo en el d e s p a c h o , viajes, d e s a y u n o s , etc. Chicos sois lo mejor, gracias por t o d a s las b u e n a s experiencias! A Esperanga, gracias por todos e s o s m o m e n t o s q u e h e m o s compartido, en los d e s a y u n o s , viajando en el coche, conversaciones, etc. han sido m u y especiales para mí. A t o d a s las extraordinarias p e r s o n a s y profesores que he tenido el placer de conocer en tantos sitios todos e s t o s años, gracias por todo lo que he a p r e n d i d o de v o s o t r o s ! A ti Przemek, has hecho de mis últimos a ñ o s un t i e m p o m u y especial. A Phil Evans, gracias por formar parte de este proceso, gracias por compartir tu conocimiento y t i e m p o conmigo. Finalmente a Gloria, d e s d e que te c o n o c í has sido una inspiración y un m o d e l o a seguir. No tengo palabras para expresar mi gratitud por estar s i e m p r e allí para mí, por compartir tu conocimiento, t i e m p o y dedicación.

Table of contents

Preface 15 R e s u m 17 R e s u m e n 19 Abstract 21

Chapter 1

Introduction and theoretical framework

1. Introduction 2 5 2. Personality 27

2 . 1 . Neuroticism 2 9

3. Stress 31 4. Cortisol 35

4 . 1 . Daytime Cortisol circadian cycle 37 4 . 1 . 1 . Cortisol a w a k e n i n g cortisol (CAR) 37

4.1.2. A r e a under the curve (AUC) 4 0

4.2. Cortisol Reactivity 4 3 5. Personality a n d cortisol: relation b e t w e e n c o n c e p t s 47

6. A P M R as an intervention to reduce stress 51

Chapter 2

Study 1 : Cortisol response under a stressful situation: Public speaking

1. Introduction 2.

3.

4.

5.

A i m M e t h o d Results Discussion

57 58 58 61 6 5

Chapter 3

Study 2: Cortisol secretion under daily situations in participants with extreme scores on neuroticism

1.

2.

3.

4.

5.

Introduction A i m

M e t h o d Results Discussion

6 9 71 71 79 85

Chapter 4

Study 3: Abbreviated Progressive Muscle Relaxation to reduce psychological and physiological stress

1.

2.

3.

4.

Introduction A i m

M e t h o d Results

89 92 92 100

5. 104

Chapter 5

Discussion, conclusions and future lines of research

1. General discussion 109

2. Limitations 117 3. Conclusion 119

3 . 1 . Future lines of research 121

References 123

Appendix

1. Personality questionnaires 149

2. Rating scales 153 3. M E M S C A P S 155 4. A A R D E X 156 5. Saliva collection device 157

6. Centrifuge for saliva s a m p l e s 158 7. Salivary s a m p l i n g protocol 159

PREFACE

T h e aim of the present PhD dissertation is to a s s e s s h o w personality traits influence the cortisol r e s p o n s e of u n d e r g r a d u a t e students in three different conditions; stressful, baseline, a n d relaxation. This w o r k starts evaluating the cortisol r e s p o n s e facing a stressful situation (public speaking) of psychology u n d e r g r a d u a t e students. T h e n continues with the study of daily cortisol (baseline cortisol) in students with extreme scores in Neuroticism (N). Finally, this dissertation e n d s with the evaluation of the efficacy of abbreviate progressive m u s c l e relaxation ( A P M R ) , to r e d u c e overall levels of both psychological a n d physiological stress in u n d e r g r a d u a t e students scoring high a n d low in N. T h e s e three studies have resulted in two publications:

• G a r c í a - B a n d a , G., Servera, M., C h e l l e w , K., Meisel, V., Fornes, J., Cardo, E., Perez, G., Riesco, M., & Doctor, R. M. (2011). Prosocial personality traits a n d adaptation to stress. Social Behavior & Personality, 39(10), 1337-1348. doi:

10.2224/sbp.2011.39.10.1337.

• G a r c í a - B a n d a , G., C h e l l e w , K., Fornes, J., Perez, G., Servera, M., & Evans, P. (2014). Neuroticism a n d cortisol: Pinning d o w n an e x p e c t e d effect.

International Journal of Psychopathology, 91, 132-138. doi:

10.1016/j.ijpsycho.2013.12.05

A n d , a future publication, w h i c h manuscript has b e e n recently submitted:

• Chellew, K., Evans, P., Fornes, J., Perez, G., & G a r c í a - B a n d a , G.

(Submitted). T h e effect of progressive m u s c l e relaxation on daily cortisol secretion. International Journal of Stress Management.

RESUM

Els trets de personalitat j u g u e n un paper rellevant en les diferencies individuals en la secreció del Cortisol. No obstant això, la naturalesa i els m e c a n i s m e s subjacents d'aquesta relació tot i r o m a n e n poc clars. El Cortisol, producte final de l'eix Hipotàlem-pituìtari-Adrenal (HPA), és un glucocorticoide que el nostre cos secreta naturalment seguint un pronunciat cicle diürn, a m b nivells elevats davant de situacions particularment estressants (reactivitat del cortisol). La present tesi doctoral té com a objectiu elucidar com els trets de personalitat influeixen en la resposta del cortisol d'estudiants universitaris en tres condicions diferents:

estressant, basal i de relaxació. A q u e s t treball c o m e n g a avaluant la resposta del cortisol davant d'una situació estressant (parlar en public) en estudiants de psicologia. E s p e r à v e m q u e la reactivitat del cortisol estigués positivament relacionada a m b Obertura, Amabilitat i Responsabilitat, i negativament a m b Extraversió, Neuroticisme i Psicoticisme. En el nostre s e g o n estudi, avaluem el perfil de secreció de cortisol basal en estudiants universitaris a m b puntuacions e x t r e m e s en Neuroticisme (N) tractant de d e m o s t r a r una associació teòrica esperat entre N i la secreció de cortisol diürn. P e n s à v e m q u e participants a m b puntuacions altes en N exhibirien c o n s t a n t m e n t nivells elevats de cortisol diürn basal c o m p a r a t a m b aquells a m b puntuacions baixes en N. Finalment, volíem e x a m i n a r si una s e t m a n a de Relaxació Muscular Progressiva A b r e u j a d a ( A P M R ) era eficag per reduir nivells totals d'estrès psicològic i fisiològic de participants a m b p u n t u a c i o n s e x t r e m e s en N.

Els nostres resultats confirmen, en primer lloc, que parlar en public a u g m e n t a significativament la secreció de cortisol en c o m p a r a c i ó a m b una activitat a c a d è m i c a

no estressant. A m é s a més, Responsabilitat ha estât a s s o c i a d a a m b un a u g m e n t significatiu dels nivells de Cortisol, i Psicoticisme a m b una a la baixa. En s e g o n lloc, trobem q u e Neuroticisme ha estat associat a m b una elevada secreció de cortisol davant de situacions d'estrès diari, e n c a r a que n o m é s d e s p r é s dels primers 4 5 min.

d e s p r é s de despertar (CAR). A q u e s t a associació ha estat independent del g e n e r e i edat dels participants, si f u m a v e n o no, l'hora de despertar, o del dia de l'estudi.

Finalment, en tercer lloc, A P M R és una eina eficaç per disminuir tant l'estrès psicológic c o m fisiológic en tots els participants, i n d e p e n d e n t m e n t de puntuacions altes o baixes en Neuroticisme, el gènere, o l'edat dels participants.

RESUMEN

Los rasgos de personalidad j u e g a n un papel relevante en las diferencias individuales en la secreción del cortisol. Sin e m b a r g o , la naturaleza y los m e c a n i s m o s s u b y a c e n t e s a esta relación a ú n p e r m a n e c e n poco claros. El cortisol, producto final del eje Hipotálamo-Pituitario-Adrenal (HPA), es un glucocorticoide que nuestro cuerpo secreta naturalmente de acuerdo a un ciclo diurno pronunciado, c o n niveles e l e v a d o s ante situaciones estresantes (reactividad del cortisol). El objetivo de la presente tesis doctoral ha sido elucidar c ó m o los rasgos de personalidad influyen en la respuesta del cortisol de estudiantes universitarios en tres condiciones distintas: estresante, basal y de relajación. Este trabajo c o m i e n z a e v a l u a n d o la respuesta del cortisol ante una situación estresante (hablar en público) en estudiantes de psicología. E s p e r á b a m o s q u e la reactividad del cortisol estuviera positivamente relacionada c o n Apertura, A m a b i l i d a d y Responsabilidad, y n e g a t i v a m e n t e c o n Extraversión, Neuroticismo y Psicoticismo. En nuestro s e g u n d o estudio, e v a l u a m o s el perfil de secreción de cortisol basal en estudiantes universitarios c o n p u n t u a c i o n e s e x t r e m a s en Neuroticismo (N). Con ello p r e t e n d í a m o s demostrar de f o r m a experimental una asociación planteada a nivel teórico entre N y secreción de cortisol diurno. A s í e s p e r á b a m o s q u e los participantes c o n p u n t u a c i o n e s altas en N exhibieran niveles elevados de cortisol diurno basal c o m p a r a d o con participantes c o n p u n t u a c i o n e s bajas en este rasgo. Por último, q u e r í a m o s e x a m i n a r si una s e m a n a de Relajación Muscular Progresiva A b r e v i a d a ( A P M R ) era efectiva en reducir los niveles totales de estrés psicológico y fisiológico de participantes c o n puntuaciones e x t r e m a s en N. Nuestros resultados confirman,

en primer lugar, que hablar en público a u m e n t a significativamente la secreción de cortisol en c o m p a r a c i ó n c o n una actividad a c a d é m i c a no estresante. A d e m á s , Responsabilidad se asoció con un a u m e n t o significativo de la respuesta de cortisol, y Psicoticismo con una respuesta a la baja. En s e g u n d o lugar, e n c o n t r a m o s q u e altos niveles de Neuroticismo se asociaron con una secreción elevada de cortisol en situaciones de estrés diario, a u n q u e solo d e s p u é s de los primeros 4 5 min d e s p u é s de despertar (CAR). Esta asociación f u e independiente del género y e d a d de los participantes, si f u m a b a n o no, de la hora de despertar, o del día del estudio. Por último, en tercer lugar, A P M R f u e eficaz en disminuir tanto el estrés psicológico c o m o fisiológico en todos los participantes, i n d e p e n d i e n t e m e n t e del género, la e d a d o de la puntuación de Neuroticismo de los participantes.

ABSTRACT

Personality traits play a significant role in individual differences in Cortisol r e s p o n s e (LeBlanc, D u c h a r m e , & T h o m p s o n , 2004). However, the nature and underlying m e c h a n i s m s of the relationship b e t w e e n cortisol secretion a n d personality traits still r e m a i n unclear. Cortisol, an end product of the Hypothalamic-Pituitary- A d r e n a l axis (HPA), is a glucocorticoid that our body naturally secretes according to a p r o n o u n c e d diurnal cycle w i t h increased values under stressful situations (cortisol reactivity). T h e aim of the present PhD dissertation w a s to elucidate how personality traits influence the cortisol secretion of u n d e r g r a d u a t e students in three different conditions; stressful, baseline, a n d relaxation. This w o r k b e g a n by evaluating the cortisol r e s p o n s e facing a stressful situation (public speaking) of psychology students. W e believed that cortisol reactivity w o u l d be positively related to O p e n n e s s , A g r e e a b l e n e s s , and Conscientiousness, a n d negatively to Extraversion, Neuroticism and Psychoticism. In our s e c o n d study, w e a s s e s s e d the baseline cortisol in students with extreme scores in Neuroticism (N) attempting to prove a theoretical e x p e c t e d association b e t w e e n N and diurnal cortisol secretion. W e postulated that high N participants w o u l d display elevated diurnal b a c k g r o u n d levels of cortisol c o m p a r e d to low N participants. Finally, w e e x a m i n e d w h e t h e r o n e w e e k of A b b r e v i a t e d Progressive M u s c l e Relaxation ( A P M R ) w a s effective in reducing overall levels of psychological a n d physiological stress of h i g h - a n d low-N participants. Our results c o n f i r m e d , firstly, that public speaking significantly increased cortisol secretion w h e n c o m p a r e d to a non-stressful a c a d e m i c activity. In addition, C o n s c i e n t i o u s n e s s w a s associated w i t h an e n h a n c e d cortisol r e s p o n s e to public

speaking, and Psychoticism with a blunted one. Secondly, w e f o u n d that high levels of Neuroticism w e r e associated with elevated cortisol secretion on daily stress, but only after the first 4 5 min following a w a k e n i n g (CAR). This association w a s independent of sex and age, s m o k i n g status, a w a k e n i n g time, a n d day of study.

Finally, in third place, A P M R w a s effective in d e c r e a s i n g both psychological and physiological stress in all participants independently of their N-score, gender, or age.

Chapter 1

Introduction and theoretical framework

1. Introduction

Traditionally, aberrant cortisol d y n a m i c s a n d personality traits have b e e n closely linked to m o o d and anxiety disorders (Oswald et al., 2 0 0 6 ) . Evidence suggests that personality traits m a y play a significant role in individual differences in cortisol r e s p o n s e (LeBlanc, D u c h a r m e , & T h o m p s o n , 2 0 0 4 ) . However, the nature a n d the underlying m e c h a n i s m s of the relation b e t w e e n cortisol secretion and personality traits still r e m a i n unclear. Cortisol, the H P A e n d product, is a glucocorticoid that our body naturally secretes according to a p r o n o u n c e d diurnal cycle with increased values under particularly stressful conditions (cortisol reactivity).

In this thesis, cortisol r e s p o n s e s to public speaking w e r e e x a m i n e d to test the hypotheses that reactivity w o u l d be positively related with o p e n n e s s , a g r e e a b l e n e s s , a n d conscientiousness, and negatively to extraversion, neuroticism and psychoticism. Moreover, there are strong theoretical a r g u m e n t s that t h o s e high on neuroticism (N) should normally exhibit higher prevailing levels of the stress-linked h o r m o n e cortisol. T h u s , in the s e c o n d study p r e s e n t e d in this thesis w e tried to prove e x p e c t e d associations b e t w e e n N a n d diurnal cortisol secretion. W e had one simple but clear theoretically derived formal hypothesis, that high N participants w o u l d constantly display elevated diurnal b a c k g r o u n d levels of cortisol c o m p a r e d to low N participants. Finally, w e w a n t e d to e x a m i n e w h e t h e r an intervention consisting of o n e - w e e k of Abbreviate Progressive M u s c l e Relaxation ( A P M R ) w a s effective in reducing overall levels of both psychological a n d physiological stress of high- and low-N participants.

In this chapter w e present a description of the m a i n concepts u s e d along this thesis that include: personality, neuroticism, stress, cortisol, daytime cortisol

circadian cycle ( C A R and A U C ) , cortisol reactivity, a n d A b b r e v i a t e d Progressive M u s c l e Relaxation ( A P M R ) . In the s e c o n d chapter, w e will introduce the three studies that form part of this thesis, a n d finally, in the last chapter w e discuss a n d highlight the m a i n results a n d limitations of t h e s e studies, reach conclusions, and suggest future lines of research that arise from this work.

2. Personality

E y s e n c k (1970) defined personality as: "A more or less stable and enduring organization of a person's character, temperament, intellect, and physique, which determines his unique adjustment to the environment. Where character denotes a person's more or less stable and enduring system of conative behaviour (will);

temperament, his more or less stable and enduring system of affective behaviour (emotion); intellect, his more or less stable and enduring system of cognitive behaviour (intelligence); physique, his more or less stable and enduring system bodily configuration and neuroendocrine endowment" (p. 243).

In this thesis w e f o c u s e d on the Eysenck's t e m p e r a m e n t aspect of personality that refers to intrapersonal processes (cognitive, emotional, and motivational) that d e t e r m i n e our individual behaviour. M o r e specifically, personality can be described as consistent behaviour patterns, stable across time and consistent across situations a n d can be quantitatively a s s e s s e d (Burger, 2011).

P a u n o n e n (1998) pointed out that t h e r e is s o m e intuitive appeal to the conceptualization that factors of personality are organized hierarchically, a r r a n g e d according to the breadth of the behaviour d o m a i n s represented (see Figure 1).

T h e r e are several a p p r o a c h e s that have a hierarchical structure to describe, explain, a n d a s s e s s personality traits. In the present thesis w e are going to present t w o of the most u s e d a n d w e l l - k n o w n models: the Eysenck's biosocial a p p r o a c h (Eysenck

& Eysenck, 1969; E y s e n c k & Eysenck, 1985a) and the psycholexical a p p r o a c h of the Five-Factor Model ( F F M ; Costa & M c C r a e , 1985).

Figure 1. Representation of a hierarchical m o d e l of personality organization. A d a p t e d from "Hierarchical organization of personality and prediction of behavior," by S. V. P a u n o n e n , 1998, Journal of Personality and Social Psychology, 74(2), p. 539. Copyright 1998 by the A m e r i c a n Psychological Association, Inc.

In both a p p r o a c h e s t w o basic personality traits are a c k n o w l e d g e d , neuroticism and extraversion. People w i t h high scores in emotional instability or 'neuroticism' dimension are moody, t o u c h y a n d anxious, w h e r e a s t h o s e with low scores are relaxed, e v e n t e m p e r e d a n d c a l m . People w i t h high scores in extraversion are enthusiastic, sociable, talkative and optimistic. O n the contrary, introverts are reserved, pessimistic a n d keep t h e m s e l v e s to themselves. E y s e n c k p r o p o s e d a third dimension called psychoticism, reflecting impulsive, antisocial, aggressive, cold, egocentric, lack of empathy, creative, a n d t o u g h - m i n d e d behaviours (Eysenck, 1 9 9 1 , 1992a, 1992b). In the F F M of Costa and M c C r a e (1985) three m o r e f u n d a m e n t a l traits w e r e i n c l u d e d : o p e n n e s s , a g r e e a b l e n e s s , a n d conscientiousness. O p e n n e s s involves active imagination, aesthetic sensitivity, attentiveness to inner feelings, preference for variety, a n d intellectual curiosity.

Characteristics s u c h as trust, straightforwardness, altruism, compliance, modesty,

a n d t e n d e r - m i n d e d n e s s are c o m p o n e n t s of a g r e e a b l e n e s s . Qualities of order, dutifulness, a c h i e v e m e n t striving, self-discipline, a n d deliberation are characteristics of conscientiousness (Costa, M c C r a e , & Dye, 1 9 9 1 ; Costa a n d M c C r a e , 1992b).

2.1. Neuroticism

T h e personality trait of neuroticism (N) refers to relatively stable t e n d e n c i e s to r e s p o n d with negative emotions to threat, frustration, or loss (Costa & M c C r a e , 1992a). Individuals in the general population vary noticeably on this trait, ranging from frequent and intense emotional reactions to minor challenges to almost non¬

emotional r e s p o n s e even if they are facing significant difficulties (Lahey, 2009). N is operationally defined by items referring to irritability, anger, sadness, anxiety, worry, hostility, self-consciousness, a n d vulnerability, w h i c h have b e e n f o u n d to be substantially correlated w i t h o n e another in factor a n a l y s e s (Costa & M c C r a e , 1992a). People w h o score low in N, contrary to people high in N, tend to be m o r e c a l m e d a n d confident, a n d a p p e a r to cope better with stress.

N is believed to reflect a stable disposition involving specific biological a n d psychological m e c h a n i s m s that produce its robust association with psychopathology.

In fact, N has b e e n s h o w n prospectively to predict the d e v e l o p m e n t of emotional disorders including major depression, posttraumatic-stress disorder (PTSD), phobias, a n d panic attacks (e.g., Breslau, Davis, & A n d r e s k i , 1995; Clark, W a t s o n , &

Mineka, 1994; H a y w a r d , Killen, K r a e m e r , & Taylor, 2 0 0 0 ; Krueger, Caspi, Moffitt, Silva, & M c G e e , 1996). In addition, f e m a l e s N scores have b e e n s h o w n to be slightly but significantly higher than in males (Costa, Terracciano, & M c C r a e , 2001),

w h i c h could explain w h y w e f o u n d m o r e w o m e n developing these type of disorders t h a n m e n .

O n e essential aspect of neuroticism is that it involves individual differences in cognition a n d information processing, producing biases, specifically, under stressful situations. In fact, high-N individuals, c o m p a r e d with low-N ones, s h o w heightened attention to negative or threatening information (rather t h a n neutral information), as e v i d e n c e d by a faster r e s p o n s e to and a slower d e t a c h m e n t from negative or threatening stimuli (Ormel et al., 2 0 1 3 ) . S u c h negative r e s p o n s e s to c h a l l e n g e s are both frequent a n d out of proportion to the c i r c u m s t a n c e s for individuals w h o are high in this trait ( M c C r a e & Costa, 2003). T h e r e f o r e in our last t w o studies w e included e x t r e m e N-scores participants (high vs. low) in order to observe better differences b e t w e e n t h e s e t w o groups.

In the next section, w e will introduce the c o n c e p t of stress and its definition, the m a i n stress sources (stressors) that could affect us. This include the description of major life events and hassles, and finally h o w w e c a n m e a s u r e t h e m .

3. Stress

Stress occurs w h e n environmental d e m a n d s o v e r w h e l m one's abilities to m e e t t h o s e d e m a n d s (Lazarus & F o l k m a n , 1984) a n d is an influential construct in health research (Keller et al., 2012). T h e interactionist model of stress (Lazarus &

F o l k m a n , 1984; Mischel, 2009) suggests a bidirectional relationship b e t w e e n an individual's r e s p o n s e a n d a stressful situation. T h e recent d e v e l o p m e n t of this model (Conger & Donnellan, 2007) differentiates b e t w e e n stress causation (stress, s u c h as life events, may lead to a c h a n g e in an individual's personality characteristics that in turn affects their r e s p o n s e to stressful events) a n d stress selection (one or m o r e individual personality characteristics may increase the d e g r e e to w h i c h a life event is e x p e r i e n c e d as stressful). In this study w e f o c u s e d in the latest one.

T h e r e are several sources of stress that c a n interfere in our lives: chronic stress, acute stress and daily stress (APA, 2014). Chronic stress refers to the constant and persisting stress stimuli over an e x t e n d e d period of time that c a n lead to psychological a n d physical debilitation and it c a n result in serious health conditions. A c u t e stress is the most c o m m o n form of stress a m o n g h u m a n s a n d , contrary to chronic stress, it refers to particular short-term stressful situations (e.g., an e x a m , an interview) that p r o d u c e s an acute stress response, but that d e c r e a s e s or disappears after the stressor is no longer available. Finally, another c o m m o n s o u r c e of stress is daily stress, w h i c h refers to minor stressful events s u c h as, daily a n n o y a n c e s a n d hassles (e.g., m a k i n g decisions, meeting deadline at w o r k or university, traffic j a m s , etc.) that are present in everybody's life. W h a t is relevant about this type of stress is that continue e x p o s u r e to them can g e n e r a t e as m u c h

d a m a g e in the long-term t h a n chronic stress. In this thesis w e focus on acute a n d daily stress b e c a u s e w e c o n s i d e r e d that both stressors are part of the student's life.

W e did not include chronic stress b e c a u s e it w o u l d n e e d s a longitudinal study design a n d w h a t w a s out of our study scope.

In relation to acute stress, w e believe that u n d e r g r a d u a t e students have frequently to f a c e several a c a d e m i c stressors (e.g., a c a d e m i c e x a m s , written assays, public s p e a k i n g , etc.), that g e n e r a t e an acute stress response. Public s p e a k i n g has been proved to be a potent social stimuli widely used in stress research (Schoofs, H a r t m a n n , & Wolf, 2008). Specifically, this task involves social evaluation by peers ( A n d r e w s et al., 2 0 0 7 ) that triggers intense emotional responses provoking c h a n g e s in HPA-axis activity a n d , consequently, eliciting strong cortisol r e s p o n s e s (Dickerson, Mycek, & Zaldivar, 2 0 0 8 ) . Therefore, in our first study w e use 10-minute-long public s p e a k i n g presentation to assess individual's stress responses.

Minor stressors are another s o u r c e of stress that people have to f a c e frequently a n d reflect the daily stress load. However, not every person will interpret t h e m as stressful or r e s p o n d in the s a m e w a y t h a n other person m a y do. T h e s e differences m a y be explained by s o m e personality traits, in particular, neuroticism (N). A s w e mention previously, people high in N are characterized by the t e n d e n c y to perceive m o r e stressors a n d to r e s p o n d negatively to these situations than people low in this trait (Lahey, 2009). T h u s , in our last t w o studies presented here, w e studied only participants with e x t r e m e N-scores to denote clearly differences b e t w e e n them in relation to daily stress.

Psychological or perceived stress c a n be a s s e s s e d by using self-reports that collect information about the number, f r e q u e n c y and intensity of the stressors e x p e r i e n c e d during a period of time (e.g., hassles, recent life experiences, etc.).

H o w e v e r t h e s e instruments present s o m e limitations, mostly d u e t o a high intra- a n d between-subjects variability in their ratings. For instance, a person w h o has to describe its level of stress in several time points could use the s a m e value but denoting s o m e t h i n g different (intra-subjects) or, two people using the s a m e score m a y signify s o m e t h i n g completely different from one participant to another ( b e t w e e n - subject). Finally, the instruments u s e d to evaluate stress m a y be not sensitive e n o u g h to denote c h a n g e s over time. Therefore, in order to obtain a reliable m e a s u r e of perceived stress w e included in our last study the S R L E scale. This scale has b e e n s h o w n to be a d e c o n t a m i n a t e d hassles m e a s u r e to determine accurately how m u c h e v e r y d a y stressors affect physical a n d mental health ( K o h n &

M a c d o n a l d , 1992), and sensitive e n o u g h to detect individual differences and c h a n g e s over time (de Jong, T i m m e r m a n , & E m m e l k a m p , 1996).

T o c o m p l e m e n t this subjective m e a s u r e (SRLE), w e also include an

"objective" m e a s u r e to increase the reliability of our results a n d , to d e m o n s t r a t e that stress is not only affecting us psychologically, but also physiologically. Indeed, w h e n w e are experiencing stress, immediately our brain g e n e r a t e s a signal that provokes a physiological r e s p o n s e activating the H P A - a x i s (e.g., G a a b , Sonderegger, Scherrer,

& Ehlert, 2006). A s a result, our organism gets ready to deal w i t h daily stress. A g o o d and reliable b i o m e a s u r e of stress is the h o r m o n e , cortisol - e n d product of HPA-axis activity.

Figure 2. Illustrates the physiological c a s c a d e involved in the hypothalamic-pituitary-adrenal (HPA) axis a n d the regulation f e e d b a c k after the cortisol secretion. A d a p t e d from Tittp://total-body- psychology.com .au/stress-response-hpa-axis/".

4. Cortisol

Cortisol is the m a i n glucocorticoid h o r m o n e responsible for mobilizing energy to deal with daily activities a n d contributes f u n d a m e n t a l l y to the m a i n t e n a n c e of basal and stress-related h o m e o s t a s i s ( M c E w e n , 2 0 0 3 ) . However, Selye (1936) recognized the paradox that the physiologic s y s t e m s activated by stress c a n not only protect and restore but also d a m a g e the body. T h e primary biological m e c h a n i s m underlying stress regulation and adaptation is the hypothalamic-pituitary-adrenal (HPA) axis (see Figure 2).

T h e H P A axis activity is g o v e r n e d by the secretion of corticotrophin-releasing h o r m o n e ( C R H ) a n d v a s o p r e s s i n (AVP) from the h y p o t h a l a m u s , w h i c h in turn activates the secretion of adrenocorticotrophic h o r m o n e (ACTH) from the pituitary, w h i c h finally stimulates the secretion of the glucocorticoids from the adrenal cortex, s u c h as cortisol. O n c e the glucocorticoids are secreted into the blood stream, they interact w i t h their receptors in multiple target tissues including the H P A axis. T h e activated glucocorticoid receptor (GR), in turn, induces a f e e d b a c k inhibition signal on both C R H a n d A V P from the h y p o t h a l a m u s a n d directly on the secretion of A C T H from pituitary that leads the reduction of H P A axis activity.

Glucocorticoids not only influence the activity of pituitary but also m a n y other functions of the central nervous system s u c h as, arousal, cognition, m o o d a n d sleep, also the activity a n d direction of intermediary m e t a b o l i s m , the m a i n t e n a n c e of a normal cardiovascular tone, the activity a n d quality of the i m m u n e a n d inflammatory reaction, including the manifestations of the sickness s y n d r o m e , as well as g r o w t h a n d reproduction ( C h r o u s o s & Kino, 2007). Glucocorticoids influence the brain, regulating the neuronal survival, neurogenesis, and sizes of c o m p l e x anatomical structures s u c h as the h i p p o c a m p u s , the acquisition of n e w m e m o r i e s and the emotional appraisal of events (Herbert et al., 2006). In that way, any generalized c h a n g e in the glucocorticoid signalling s y s t e m w o u l d be followed by corrective, c o m p e n s a t o r y c h a n g e s in the activity of the H P A axis.

However, s o m e t i m e s this "compensatory" activity does not occur. In fact, w h e r e a s cortisol generally helps the organism f a c e daily life activities, disturbed patterns of cortisol secretion are potentially detrimental in long-term, for instance, the deregulation of d a y t i m e cortisol activity has indeed been associated w i t h s t r e s s -

related pathologies, including depression, post-traumatic stress disorder, anxiety, externalizing behaviours, a n d cognitive deficits, as occur with chronic stress.

4.1. Daytime Cortisol circadian cycle

Daytime cortisol cycle refers to the cortisol secreted along the day. T h e cortisol secretion presents a circadian rhythm of 2 4 hours that follows a characteristic diurnal rhythm with several secretory e p i s o d e s of short duration and high amplitude (Fries, Dettenborn, & Kirschbaum, 2009). Under normal conditions, the typical diurnal cortisol profile s h o w s a sharp rise upon a w a k e n i n g , called cortisol a w a k e n i n g r e s p o n s e (CAR), w h e r e thereafter there is a steady decline over the rest of the day with lower levels in the evening and night (Tsigos & Chrousos, 2002). T h e C A R a p p e a r s to be a distinct feature of the hypothalamus-pituitary-adrenal (HPA) axis, s u p e r i m p o s i n g the circadian rhythmicity of cortisol secretion (Fries, Dettenborn,

& K i r s c h b a u m , 2009) as it a d d s a substantial incremental effect to the linear trend of increasing cortisol concentrations in the early m o r n i n g hours (Wilhelm, Born, Kudielka, Scholtz & Wust, 2007). M o r e importantly, the a w a k e n i n g itself is a consistent, recurring, a n d strong stimulus for H P A activity (Wilhelm et al., 2007).

4.1.1. Cortisol Awakening Response (CAR)

T h e C A R is a discrete a n d distinctive part of the cortisol circadian cycle. In healthy adults salivary free cortisol concentrations increase by b e t w e e n 50 and

s1

1.25-

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.50"

I \u

s3

.25" i i

: :

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: :

s4

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Time from awakening (hours)

Figure 3. Characteristic of the cortisol diurnal profile during 12hs period w h e r e the Cortisol A w a k e n i n g R e s p o n s e (CAR) is represented, b e t w e e n 0h (wake-up) and first 4 5 minutes (0.75h) after a w a k e n i n g .

Pruessner et al. (1997) w e r e the first w h o p r o p o s e d that the repeated a s s e s s m e n t of this cortisol increase after a w a k e n i n g in saliva m i g h t represent a useful a n d e a s y index of cortisol regulation. I n d e e d , the C A R has b e e n attracting 1 6 0 % in the first 30-45 min immediately p o s t - a w a k e n i n g (approximate average increase of 9 nmol/l, range 4 - 1 5 nmol/l, estimated to be equivalent, to about three secretory episodes; Clow, T h o r n , Evans, & Hucklebridge, 2004). This r e s p o n s e w a s coined the "Cortisol A w a k e n i n g R e s p o n s e " (CAR) by F e d e r e n k o et al. in 2 0 0 4 (see F i g u r e 3).

attention from researchers for a n u m b e r of reasons. First, the C A R is o n e of the most important a n d e a s y p a r a m e t e r of H P A axis function to measure. S e c o n d , the C A R is under s o m e w h a t independent control from cortisol output d u r i n g the remainder of the day, a n d associations b e t w e e n the C A R a n d cortisol s a m p l e d later in the day are quite low (Edwards, Evans, Hucklebridge, & Clow, 2 0 0 1 ) . Third, twin studies have d o c u m e n t e d a genetic influence o n the C A R that is distinct from the heritability of daytime cortisol levels (Kupper et al., 2005). Finally a n d very important, the m a g n i t u d e of the C A R a p p e a r s to be associated with psychosocial factors a n d health in potentially significant w a y s . In fact, Chida and Steptoe (2009) suggest that the m a g n i t u d e of the C A R m a y be a distinctive indicator of H P A function a n d dysfunction.

Early psychological studies of the C A R indicated that the r e s p o n s e w a s heightened a m o n g individuals experiencing job stress, overload, and low self-esteem (Schulz, K i r s c h b a u m , Pruessner, & Hellhammer, 1998; Pruessner, Hellhammer, &

K i r s c h b a u m , 1999; W ü s t , Federenko, Hellhammer, & K i r s c h b a u m , 2000). Others suggest that the C A R might be a n indicator of chronic psychosocial stress (e.g., B h a g w a g a r , Hafizi, & C o w e n , 2005). Furthermore, larger C A R s w e r e s u g g e s t e d to be a m a r k e r of neuroendocrine activation as the individual c o n t e m p l a t e d the challenges of the day a h e a d (Chida and Steptoe, 2 0 0 9 ) . B y contrast, a diminished C A R a p p e a r e d to be present in people suffering from post-traumatic stress disorder (de Kloet et al., 2 0 0 6 ; W a h b e h & O k e n , 2013), m e n with systemic hypertension (Wirtz et al., 2007), and w o m e n with mild or m o d e r a t e d e p r e s s i o n (Stetler & Miller, 2005).

N o n e t h e l e s s , the C A R is particularly volatile a n d variable intra- a n d b e t w e e n - subjects. This variability has b e e n reported at the a w a k e n i n g time but not later during the day (Kupper et al., 2 0 0 5 ) a n d may be affected by biological m e c h a n i s m s of control. T h e s e m e c h a n i s m s are the suprachiasmatic nucleus circadian clock (Postnova, Fulcher, B r a u n , & R o b i n s o n , 2013), the h i p p o c a m p a l regulation (Fries et al., 2009), a n d biological p r o c e s s e s associated with s l e e p - w a k e cycles (Smyth, Clow, T h o r n , Huckebridge, & Evans, 2013). Therefore, in our s e c o n d a n d third study, d u e to the fact that cortisol secretion during the first 45 min is too volatile, w e also evaluated the area under the curve (AUC), w h i c h represents the total cortisol secreted during a predefined period of time, w h i c h s e e m s to be m o r e stable than the C A R to evaluate c h a n g e s over time.

4.1.2. Area under the curve (AUC)

T h e area under the curve (AUC) is another cortisol secretion parameter that provides relevant information about the functioning of HPA. T h e A U C is often u s e d to estimate total cortisol secretion during a predefined time period ( H a n s e n , G a r d e , &

Persson, 2008). In research a n d clinical settings, t h e salivary cortisol m e a s u r e s are u s e d as a physiology indicator of responsiveness of the H P A axis to determine the health c o n s e q u e n c e s of stress.

In research involving repeated m e a s u r e m e n t s of a r e s p o n s e variable, there is a need to derive parameters that s u m m a r i z e the information c o n t a i n e d in the multivariate data. T h e A U C is a g o o d p a r a m e t e r to get this information a n d it is c o m p u t e d following a trapezoidal f o r m u l a separated into triangles and rectangles.

Figure 4. T i m e c o u r s e of an artificial dataset with six m e a s u r e m e n t s ; the triangles a n d rectangles illustrate the composition of the area under the curve (AUC). 'ml' to 'm6' denote the single m e a s u r e m e n t s , a n d ' t 1 ' to 't5' denote the time interval b e t w e e n the m e a s u r e m e n t s . A d a p t e d from "Two formulas for computation of the area under the curve represent measures of total hormone concentration versus time-dependent change" by J. C. Pruessner, C.

K i r s c h b a u m , G. M e i n l s c h m i d , a n d D. H. Hellhammer, 2003, Psychoneuroendocrinology, 28, p. 918. Copyright 2 0 0 3 by Elsevier Science L t d .

Pruessner, K i r s c h b a u m , M e i n l s c h m i d , & H e l l h a m m e r (2003) provide a simple f o r m u l a for the c o m p u t a t i o n of t w o types of A U C that reveal different information (see Figure 4): A U C g (area under the curve to the ground) and A U C i (area under the curve to the increase).

AUC^q =

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' = ( |

'

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In this study w e f o c u s e d o n t h e A U C g p a r a m e t e r a n d w e divided it in t w o different parameters: A U C 0 _ 4 5 m i n (the area under t h e curve the first 4 5 m i n after a w a k e n i n g ) a n d A U C 0 7 5 h _ 1 2 h (also called "total Cortisol secretion" - T C S in o u r last study), w h i c h represent t h e cortisol secreted during t h e remainder of t h e 12h period after C A R (see F i g u r e 5 ) .

T h e A U C i is calculated with reference to the baseline m e a s u r e m e n t a n d it ignores t h e distance from zero for all m e a s u r e m e n t s a n d e m p h a s i z e s t h e c h a n g e s over t i m e . A U C g is t h e total area under t h e c u r v e , a n d it takes into a c c o u n t both sensitivity (the difference b e t w e e n t h e single m e a s u r e m e n t s from e a c h other) a n d intensity (the distance from t h e s e m e a s u r e s from ground), a n d it is a s s u m e d to be a m e a s u r e m o r e related to total h o r m o n e o u t p u t .

B o t h f o r m u l a s a r e basically s i m p l e additions of areas consisting of triangles a n d r e c t a n g l e s :

AUCO 45min AUC075h_12h

0.00h 0.75h 2.50h 8.00h 12.00h 0.00h 0.75h 2.50h 6.00h 12.00h Time from awakening (hours) Time from awakening (hours)

Figure 5. Plots s h o w i n g t w o f o r m s of A U C g : A U C 0 _ 4 5 m i n and A U C 0 7 5 h _ 1 2 h or T C S .

W e have described how the cortisol diurnal profile normally b e h a v e s under daily situations a n d several w a y s to assess the functioning of H P A - a x i s o b t a i n e d from saliva s a m p l e s . H o w e v e r , this d a y t i m e cortisol profile can be s u p p l e m e n t e d by episodic Cortisol reactivity to unpredictable, uncertain, and novel psychological challenges (Bosch et al, 2009).

4.2. Cortisol Reactivity

T h e HPA-axis is a major endocrine system adapting the organism to bodily a n d e n v i r o n m e n t a l challenges b y inducing b e h a v i o r a l a n d physiological c h a n g e s , improving the organism's ability to adjust h o m e o s t a s i s (Tsigos & Chrousos, 2002).

Cortisol plays a crucial role in the organism's efforts to adjust to these c h a l l e n g e s . In fact, under unpredictable, uncertain, and novel challenges an increase in cortisol secretion is considered an adaptive r e s p o n s e to a m i s m a t c h b e t w e e n the individual

needs and factors in the e n v i r o n m e n t (de Kloet, 2 0 0 3 ; M c E w e n , 2000). This reactivity has widely b e e n considered an endocrine index of the stress r e s p o n s e (Miller, C h e n , & Cole, 2009). However, s o m e studies have been f o u n d that not always there is an increase in the cortisol r e s p o n s e during the acute stressful situation, but also a flat or blunted cortisol r e s p o n s e (e.g., Loft et al., 2 0 0 7 ; Roy, 2 0 0 4 ; Saxbe, Repetti, & Nishina, 2 0 0 8 ) , w h i c h have b e e n associated with a poor or less adaptive response.

A n excessive d e m a n d over time on energy mobilization d u e to frequent stress, failed s h u t d o w n of the stress reactivity system or inadequate r e s p o n s e to challenges, generates an allostatic load ( M c E w e n , 1 9 9 8 ) . M c E w e n (2000) define allostatic load as a result of the effort that our body as to tolerate trying to keep the allostasis (homeostasis) during stressful d e m a n d s . This load at s o m e point might affect not only the H P A axis function ( M c E w e n , 2 0 0 8 ; O s w a l d et al., 2006), but also the a u t o n o m i c nervous system function (Appelhans & L u e c k e n , 2 0 0 6 ; Chida &

Hamer, 2 0 0 8 ; Thayer, A h s , Fredrikson, Sollers, & W a g e r , 2011), a n d produce c h a n g e s in the structure of the brain with a decline of cognitive functions (Herbert et al., 2 0 0 6 ; M c E w e n , 2 0 1 2 ; Lupien, M c E w e n , Gunnar, & Heim, 2009). Concretely, the a c c u m u l a t i o n of this load (called overload by M c E w e n ) s o m e t i m e s lead to target tissue pathology, as occurs in chronically stressed or d e p r e s s e d individuals ( C h r o u s o s 2 0 0 0 ; Gold & Chrousos, 2002).

A l t h o u g h all h u m a n beings e n c o u n t e r stressful events, they do not respond identically to s u c h experiences. W h e r e a s s o m e individuals adapt flexibly to the c h a n g i n g d e m a n d s of stressful experiences, others cope far less effectively. T h u s , in relation to t h e s e differences in cortisol responses, a large n u m b e r of studies have f o u n d a substantial inter- a n d intra-individual variability to similar challenges (Chida &

Steptoe, 2 0 0 9 ; Kudielka, Hellhammer, & Wüst, 2 0 0 9 ; T h o r n , Hucklebridge, Evans, &

Clow, 2 0 0 9 ) and it has b e e n s u g g e s t e d that personality traits m a y play a significant role in their explanation (LeBlanc, D u c h a r m e , & T h o m p s o n , 2 0 0 4 ; O s w a l d et al., 2 0 0 6 ; Pruessner et al., 1997).

5. Personality and Cortisol: relation between concepts

W h e n e v e r the brain needs energy, the HPA-axis will help to allocate glucose to the brain, increasing this d y n a m i c (higher Cortisol peaks) under stressful conditions (Peters et al., 2004). A s w e m e n t i o n e d above, there is s o m e inter- a n d intra-individual variability in cortisol secretion, a n d part of this variability m a y be explained by personality traits. Associations b e t w e e n cortisol a n d personality have been f o u n d under stressful situations (acute stress) a n d under daily activities (daily stressors).

In relation to acute stress, associations b e t w e e n neuroticism a n d elevated urinary cortisol have been d o c u m e n t e d in a c a d e m i c e x a m s (Garcia de la Banda, M a r t i n e z - A b a s c a l , Riesco, & Perez, 2 0 0 4 ) a n d mental arithmetic tasks (Habra, Linden, A n d e r s o n , & W e i n b e r g , 2 0 0 3 ) . O n the contrary, neuroticism w a s also linked to blunted salivary cortisol r e s p o n s e s to public s p e a k i n g (Garcia de la Banda, Martinez-Abascal, Pastor, et al., 2 0 0 4 ) , mental arithmetic tasks (Phillips, Carroll, Burns, & Drayson, 2005), and cold e x p o s u r e (LeBlanc & D u c h a r m e , 2005). T h e r e are also other personality traits that have b e e n related with cortisol. A diminished cortisol response to stress has been linked to extraversion (Garcia de la Banda, M a r t i n e z - A b a s c a l , Pastor, et al., 2 0 0 4 ; Kirschbaum et al., 1995; O s w a l d et al., 2006), but directionally opposite results have been reported by LeBlanc a n d D u c h a r m e (2005). O p e n n e s s has b e e n linked to higher cortisol levels e v a l u a t e d by the Trier Social Stress Test (TSST; K i r s c h b a u m , Pirke, & Hellhammer, 1993), while participants low in a g r e e a b l e n e s s (who tend to be mistrusting a n d hostile) secreted m o r e cortisol c o m p a r e d to people that have higher scores in a g r e e a b l e n e s s (in males; Suarez, K u h n , S c h a n b e r g , Williams, & Z i m m e r m a n , 1998).

O n the contrary, conscientiousness, considered a buffer for stress (Korotkov, 2008) a n d a g o o d predictor of health and longevity (Friedman, 2008), has not been associated with cortisol secretion (Nater, H o p p m a n , and Klumb, 2010; O s w a l d et al., 2 0 0 6 ; Schoofs, H a r t m a n n , & Wolf, 2008). Finally, no association has b e e n f o u n d in previous studies b e t w e e n psychoticism a n d cortisol ( K i r s c h b a u m , Bartussek, &

Strasburger, 1992; S c h o m m e r , Kudielka, Hellhammer, & K i r s c h b a u m , 1999).

In relation to daily stress, a small body of research has tried to relate basal cortisol a n d personality. In particular, the trait of neuroticism. In fact, neuroticism has b e e n not only associated to psychological stress but also with excessive cortisol secretion that predisposes individuals to p s y c h o p a t h o l o g y (Lahey, 2 0 0 9 ; O r m e l et al., 2013). However, the direction of this association r e m a i n e d inconclusive, since s o m e studies f o u n d increased, s h o w i n g individuals with high N scores to have greater cortisol levels (Nater, H o p p m a n n , & Klumb, 2 0 1 0 ; Portella, Harmer, Flint, C o w e n , & G o o d w i n , 2005) a n d others d e c r e a s e d cortisol concentrations (Hauner et al., 2 0 0 8 ; LeBlanc & D u c h a r m e , 2005). In addition, Mikolajczak et al. (2010) f o u n d that high N w a s associated with significantly less flexibility of the C A R , w h e n w e e k e n d a n d w e e k d a y profiles are c o m p a r e d . Also a flatter diurnal cortisol slope has b e e n linked to higher N, but only in male participants (Hauner et al., 2 0 0 8 ) . Nonetheless, in a majority of studies, the predicted link b e t w e e n high N a n d high basal cortisol it has not been f o u n d (Adler, W e d e k i n d , Pilz, Weniger, & Huether, 1997; C h a n , G o o d w i n , & Harmer, 2 0 0 7 ; Ferguson, 2 0 0 8 ; Gerritsen et al., 2 0 0 9 ; Hill, Billington, & Krägelog, 2 0 1 3 ; Riese, Rijsdijk, R o s m a l e n , Snieder, & O r m e l , 2 0 0 9 ; S c h o m m e r , Kudielka, Hellhammer, & Kirschbaum, 1999; V a n Santen et al., 2011).

This generally inconsistent picture in regard to personality a n d cortisol might partly reflect methodological differences. For e x a m p l e , early researchers used the

E y s e n c k Personality Q u e s t i o n n a i r e - R e v i s e d (EPQ-R; E y s e n c k & Eysenck, 1985b) to a s s e s s personality m e a s u r e s ( S c h o m m e r et al., 1999) while later researchers relied on the N E O Personality Inventory (Costa & M c C r a e , 1985) or selected other personality questionnaires s u c h as the Freiburg Personality Inventory (Fahrenberg, H a m p e l , & Selg, 1989) used by Brandtstädter, Baltes-Götz, K i r s c h b a u m , and H e l l h a m m e r (1991). In our three studies w e include both questionnaires to solve this problem a n d to g u a r a n t e e the reliability of our results. A n o t h e r problem is that in s o m e studies laboratory stressors have b e e n u s e d with a lack of independent validation of their stress-eliciting properties. S p e a k in front of an audience, is a proven social stressor a n d has b e c o m e c o m m o n l y u s e d in the study of stress (Schoofs, H a r t m a n n , & Wolf, 2008). Therefore, in our first study w e u s e d 10-minutes public presentation as an acute stressor to a s s e s s the stress response.

A rigorous a s s e s s m e n t of cortisol is critical in this type of studies as well.

However, w h e n cortisol reactivity has b e e n a s s e s s e d , only a pretest a n d posttest m e a s u r e has been typically u s e d . M a n y studies u s e d the first saliva s a m p l e , before the stressful situation, as a pretest condition, without taking into consideration that this cortisol level value m a y be influenced by anticipation. Therefore, in both stressful a n d basal cortisol studies w e include baseline m e a s u r e s of cortisol a w e e k before to the specific situation (acute or daily stress), to control the effect of anticipation or novelty respectively.

Additionally, m a n y researchers exploring personality a n d cortisol activity have relied on s a m p l e s consisting of either adults or very y o u n g children ( B o u m a , Riese, O r m e l , Verhulst, & Oldehinkel, 2009). W e consider that late a d o l e s c e n c e represents the ideal time for the evaluation of cortisol, because is the period before personality a n d cortisol patterns have b e e n further affected by a long history of major life events

or psychopathology, permitting a relatively "clean" observation of the inter-correlation pattern b e t w e e n cortisol a n d personality traits (Hauner et al., 2008). For that reason this population has been our target s a m p l e in the three studies.

In s u m , w e have used both personality questionnaires, naturalistic a c a d e m i c settings to a s s e s s acute stress, including baseline cortisol m e a s u r e s in all studies, a n d f o c u s e d on y o u n g population. In addition, in our s e c o n d and third study, w e u s e d both electronic monitoring devices a n d m a n u a l registration of the exactly time w h e n e a c h saliva s a m p l e w a s collected to increase compliance. W e included as well several control features that could be affecting cortisol secretion, s u c h as stress level, f o o d or drinks intakes, s m o k i n g status, medication, etc. Finally, s a m p l e characteristics w e r e also c o n t r o l l e d : similar n u m b e r of participants in relation to sex, participant's h o m o g e n e i t y in age a n d education, a n d careful selection of e x t r e m e high versus low scores in neuroticism.

6. APMR as an intervention to reduce psychological and physiological stress

Relaxation is a behavioural intervention used to release bodily tensions a n d p r o m o t e positive feelings to deal with stressors. Relaxation is one of the primary c o m p o n e n t s of all kinds of meditation, w h i c h induce a pleasant a n d d e e p relaxed state of body a n d mind (Hussain & B h u s h a n , 2010). More importantly, relaxation t e c h n i q u e s are a central c o m p o n e n t in most c o m p r e h e n s i v e p r o g r a m s for the treatment of stress-related problems ( B e n s o n , Beary & Carol, 1974), w h i c h is the f o c u s of our study.

J a c o b s o n (1938) discovered that by systematically tensing and relaxing different m u s c l e groups a n d by learning to f o c u s on and discriminate b e t w e e n the resulting sensations of tension a n d relaxation, a person m a y almost alleviate m u s c l e contractions a n d experience a feeling of d e e p relaxation (Bernstein & Borkovec, 1973). Progressive M u s c l e Relaxation (PMR) training p r o d u c e s extraordinarily low levels of m u s c l e tension, a n d that patients suffering from a variety of psychological a n d somatic disorders e x p e r i e n c e significant relief w h e n they practice this t e c h n i q u e (Lehrer, 1978). However, even w h e n P M R w a s originally c o n c e i v e d by J a c o b s o n , requiring m o r e t h a n 40 individual sessions, w a s not until 1973 w h e n Bernstein and Borkovec streamlined J a c o b s o n ' s training a p p r o a c h a n d specified in a step-by-step m a n n e r the procedures for administering relaxation training to clients in 8 to 12 sessions. Bernstein a n d Borkovec provided a protocol called A b b r e v i a t e d Progressive M u s c l e Relaxation ( A P M R ) , that involves shorter sessions and only 16 m u s c l e groups rather than the nearly 30 indicated by J a c o b s o n .

A P M R is o n e the most t e c h n i q u e s used with a long history of studies s h o w i n g positive results b a s e d on clinical population with several d i s e a s e s and sub-clinical population. Certainly, A P M R has s h o w n to produce effective psychological c h a n g e s w h i c h include, r e d u c e d anxiety levels ( R a u s c h , Gramling, & A u e r b a c h , 2006), d e c r e a s e d perceived stress (Emery, France, Harris, N o r m a n , & V a n A r s d a l e n , 2008) a n d increased feelings of relaxation (Pawlow & Jones, 2002), a n d physiological benefits, s u c h as d e c r e a s e d cortisol levels (Krajewski, S a v e r l a n d , & W i e l a n d , 2 0 1 1 ; P a w l o w & Jones, 2 0 0 2 , 2005).

Due to its historical pedigree, its well-defined a n d easily taught procedures, its comparatively low cost delivery, a n d s o m e evidence of efficacy, A P M R has b e c o m e justly popular as a promising stress-reduction intervention. Given s u c h promise, it is an ideal candidate for m o r e detailed scrutiny of its efficacy. However, mostly of the existing studies that assess c h a n g e s in cortisol present s o m e limitations in their designs. For instance, using only a single session of A P M R for 2 0 min and just one cortisol m e a s u r e t a k e n immediately before and after (Dolbier & R u s h , 2 0 1 2 ; P a w l o w

& Jones, 2005), or applying t w o A P M R sessions s p a c e d s e v e n d a y s apart, but again a s s e s s i n g cortisol immediately before a n d after each session ( P a w l o w & Jones, 2002), or using g o o d cortisol m e a s u r e s but very small s a m p l e size (n=7) in both control a n d experimental g r o u p s (Krajewski et al., 2011). So, even w h e n in e s s e n c e all these studies are positive in suggesting that cortisol d e c r e a s e s immediately before and after A P M R sessions (Dolbier & R u s h , 2 0 1 2 ; P a w l o w & Jones, 2 0 0 2 , 2005) or during a s i x - m o n t h period of daily practice (Krajewski et al., 2011), n o n e of t h e s e studies e x a m i n e c h a n g e s in m e a s u r e s designed to be stable e s t i m a t e s of prevailing cortisol levels, s u c h as A U C , in a meaningful period o n e - w e e k before a n d after a well-controlled intervention.

Therefore, in our last study, a carefully constructed cortisol m e a s u r e (TCS) a n d an appropriate self-report (SRLE) w a s u s e d in order to provide a robust physiological a n d psychological markers of stress. W e investigated w h e t h e r 5 consecutive d a y s of A P M R training impacts on 'prevailing' levels of stress c o m p a r i n g o n e - w e e k before and o n e - w e e k after the intervention, rather t h a n just its efficacy in reducing spot m e a s u r e s of stress from start to finish a single session of A P M R . W e also e x a m i n e w h e t h e r the efficacy of this intervention m a y be m o d u l a t e d by neuroticism.

Chapter 2

Cortisol response under a stressful situation: Public

speaking

Introduction

Cortisol, e n d product of the HPA-axis, follows a circadian rhythm (24 hours) of secretion with a significant peak in the first 0.75h after a w a k e n i n g allowing us to f a c e daily activities. However, this basal rhythm is s u p p l e m e n t e d by episodic cortisol reactivity under stressful situations. Current research s h o w s that university is a very stressful time for at least 5 0 % of the student body (Regehr, Glancy, & Pitts, 2013).

Potential stressors derive from the need to adjust to heavy a c a d e m i c d e m a n d s a n d the n e e d for students to i m m e r s e t h e m s e l v e s in a novel social network (Dolbier &

Rush, 2012). Public speaking is o n e of the most frequent stressors students e x p e r i e n c e during their a c a d e m i c training and is a proven social stressor u s e d to a s s e s s cortisol reactivity. Finally, w e have described previously that personality plays a significant role in the w a y people react under similar stressful conditions, and therefore s o m e of these traits are associated with differences in cortisol response to challenge. However, in prior research several inconsistencies have been f o u n d in the relationship b e t w e e n personality a n d cortisol reactivity that might partly reflect s o m e methodological issues.

T h e r e f o r e in our study w e w a n t e d to control several factors that in our opinion might help to clarify s o m e of these inconsistencies. First, in order to increase the validity of personality a s s e s s m e n t , w e u s e d both E P Q - R a n d N E O - F F I questionnaires. S e c o n d , w e u s e d a 10-minute-long class public presentation to evaluate cortisol response, as a students' real life stressor (opposite to laboratory stressors). Third, in order to increase methodological rigor w e include additional baseline cortisol sampling t a k e n on a previous day to the stressful situation but at the

s a m e time that the public speaking s a m p l e s w e r e t a k e n . Finally, b e c a u s e late adolescent represents the period before personality a n d cortisol patterns have been further affected by a long history of major life events or psychopathology, will permit us a "clean" observation of the relationship b e t w e e n cortisol a n d personality, w e f o c u s e d on this group population.

S u m m i n g up, the aim of this first study w a s t o c o m p a r e salivary cortisol secreted by a group of university students in two different c o n d i t i o n s : non-stressful a n d stressful. Differences in cortisol reactivity will be correlated with personality traits. Our first hypothesis w a s : public speaking (stressful condition) will increase cortisol secretion c o m p a r e d with a daily a c a d e m i c activity (baseline condition). W e anticipated also that cortisol reactivity w o u l d be positively related to O p e n n e s s , A g r e e a b l e n e s s a n d Conscientiousness, and negatively related to Extraversion, Neuroticism a n d Psychoticism.

M e t h o d

Participants

Seventy-five students from University of Balearic Islands (UIB) participated in our study, 56 w e r e w o m a n a n d 19 w e r e m e n ( m e a n age = 2 0 . 9 years). All w e r e volunteers enrolled in a Psychology of Personality class at UIB across three a c a d e m i c intakes with no exclusion criteria except the provision of both c o m p l e t e questionnaire a n d c o m p l e t e cortisol data.

Instruments

- Participants c o m p l e t e d the 83-items of the S p a n i s h version of the E y s e n c k Personality Q u e s t i o n n a i r e - R e v i s e d (EPQ-R; E y s e n c k & Eysenck, 1997), using a d i c h o t o m o u s y e s / n o response. This questionnaire provides three major personality dimensions: Extraversion (E), Neuroticism (N) a n d Psychoticism (P).

- Participants also c o m p l e t e d t h e revised short-form version of t h e S p a n i s h N E O Five Factor Inventory ( N E O - F F I ; Costa & M c C r a e , 1999). This inventory consists in 60-items of w h i c h m e a s u r e the five major personality d i m e n s i o n s : Neuroticism (N), Extraversion (E), O p e n n e s s (O), A g r e e a b l e n e s s (A) a n d C o n s c i e n t i o u s n e s s (C). Participants r e s p o n d e d on a 5-point Likert scale from 0 (totally disagree) to 4 (totally agree).

Procedure

A t t h e start of the semester, students c o m p l e t e d t h e E P Q - R a n d t h e N E O - F F I scales, a n d after providing written informed consent, f o u r salivary s a m p l e s w e r e t a k e n to a s s e s s cortisol levels during t h e late afternoon (between 4 a n d 6 pm). T w o baseline s a m p l e s w e r e t a k e n on a day during a class period w h e r e t h e student had no paper, examination, or class participation at approximately t h e s a m e time w h e n t h e s a m p l e s w e r e t a k e n during the stressful day. T w o stress s a m p l e s w e r e t a k e n for e a c h participant during a class performance, w h e r e t h e student providing t h e s a m p l e had to give a 10-minutes presentation to the class a n d a n s w e r classmates' questions after t h e presentation. T h e first s a m p l e w a s t a k e n just prior t h e presentation and the s e c o n d 30-minutes after (see Figure 1).