Implications

The findings in this thesis may have implications for how sleep disturbances are related to clinical outcome, for clinical practice and for a transdiagnostic understanding of sleep disturbances.

Clinical implications

First and foremost, the high frequency of sleep disturbances in and across severe mental disorders, together with their association to clinical symptoms, poorer functioning and cognitive impairment, underlines the need for more attention regarding assessment and treatment of sleep disturbances.

Two recent studies found clinicians to be highly aware that sleep disturbances are common in people with severe mental disorders (Barrett et al., 2020; Rehman et al., 2017). The former study was even based on data including the catchment areas from which recruitment was carried out in the studies in this thesis. Nevertheless, the studies found that sleep disturbances are rarely assessed and treated according to guidelines. Rather, information about sleep hygiene and medications such as

antihistamines or hypnotics were used despite indications that these treatments have very limited effects (Kallestad et al., 2011; Rehman et al., 2017). Thus, there is an obvious gap between the need for sleep treatments in severe mental disorders and the treatment offered, despite current

recommendations that sleep disturbances should be assessed and treated irrespective of other psychiatric comorbidities (American Psychiatric Association, 2013).

Recently there has been a call from user-organizations, demanding that more research findings are translated into clinically useful treatments. The idea of precision psychiatry - to choose “the right treatment for the right person at the right time” – is also taking hold. The clinical implications of this thesis are in line with these emerging ideas. National barriers to implementation of evidence based interventions for treating sleep disturbances such as Cognitive Behavioral Therapy for insomnia (CBTi) and light therapy for circadian rhythm disorders have been identified, and include lack of knowledge about sleep assessment and treatment, beliefs that sleep treatment is too resource

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demanding and that patients lack motivation for treatment (Barrett et al., 2020). Yet, studies have shown that these are barriers that we may overcome with more knowledge (Freeman et al., 2015;

Sheaves et al., 2017). Thus, educating health personnel, both about sleep assessment and about the ease and effectiveness of treatment, is needed. CBTi is an approved method for treating chronic insomnia consisting of several components, including sleep hygiene, stimulus control, sleep

restriction, cognitive techniques and relaxation training. CBTi has shown to significantly improve not only sleep, but also affective symptoms, psychotic symptoms such as paranoia and hallucinations in addition to functioning (Freeman et al., 2017; Harvey et al., 2015; F. Waite et al., 2016; Waite, Sheaves, Isham, Reeve, & Freeman, 2019). Even more importantly, a randomized controlled trial suggests that treatment of sleep disturbance may also improve cognitive functioning (Kanady et al., 2017). The latter is especially important, given that there are few treatment options besides

cognitive remediation therapy that effectively target cognitive impairments in severe mental disorders. Thus, it is time to take research into practice and improve sleep health by implementing evidence-based sleep treatment to those in need of it.

Another important clinical implication of the results presented in this thesis is the need for better tailoring of medications. Medications with sedative effects were partly, but not entirely, found to explain the high frequency of hypersomnia. As we also found that the frequency of such medication is high in severe mental disorders, an important clinical implication is to change or reduce this type of medication, which in turn may effectively reduce hypersomnia rates. This is a particularly salient point given the fact that current knowledge regarding efficient treatment options for hypersomnia is scarce.

Because the frequency of medication with sedative effects was significantly higher in first-treatment bipolar disorder compared to first-treatment schizophrenia, better medication tailoring is especially important in early phases of bipolar disorder. Furthermore, poorer performance on all cognitive domains were significantly associated with the use of medication with sedative effects, except for

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attention and flexibility. Thus, reducing the use of medication with sedative effects is also important in terms of improving cognitive impairment.

Finally, when treating people with severe mental disorders with childhood trauma experiences, clinicians should be especially aware of the risk for sleep disturbances. Treating insomnia may here be important to reduce the long-term effect of childhood trauma experiences. Also, carefully building the dynamics of childhood trauma into sleep treatment by e.g. addressing and treating nightmares will be important (Sheaves et al., 2016).

Transdiagnostic implications

The majority of studies on mental illness and sleep are disorder specific, meaning that each study is focused on treating one type of sleep disturbance (typically insomnia) within a specific disorder. A major implication of this thesis is, however, that sleep disturbances are transdiagnostic phenomena with transdiagnostic associations to clinical symptoms, dysfunction and cognitive impairments and therefore should be treated accordingly. There are several advantages of viewing sleep disturbances as transdiagnostic phenomena. Importantly, it implies that one may transfer knowledge about sleep disturbances from one diagnostic category to another. If sleep disturbances and symptoms in schizophrenia spectrum disorders are influencing each other (i.e. insomnia and psychotic or depressive symptoms), it follows that interventions for sleep disturbances may improve these symptoms across disorders (Harvey et al., 2011). These arguments are at the core of a novel treatment approach that has been introduced in the period we were planning and executing the studies in this thesis, the Transdiagnostic Sleep and Circadian Intervention (TranS-C) (Harvey &

Buysse, 2017). The tranS-C is based on supplementing CBTi with elements from three other evidence-based treatments; interpersonal and social rhythm therapy, chronotherapy and motivational

interviewing. With a theoretical perspective on sleep that promotes sleep health, the aim is to promote optimal sleep across psychiatric disorders, in six dimensions; regularity, satisfaction with sleep, alertness (during daytime), timing, efficiency and duration. In this sense sleep health is relevant to all individuals, irrespective of the presence of a clinical sleep disorder or not. However,

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although showing promising results (Dong, Dolsen, Martinez, Notsu, & Harvey, 2019; Harvey et al., 2016; Harvey et al., 2015) large-scale evaluation of the approach is needed. Nonetheless, more research into the effects of implementing TranS-C (thus promoting good sleep health) in severe mental disorders is exciting, given the knowledge that poor sleep quality is linked to several areas of compromised health common in severe mental disorders, including cardiac health (Javaheri &

Redline, 2017; Ringen, 2020).

In study III we found that sub-types of childhood trauma were differentially linked to insomnia in schizophrenia and bipolar disorder, with several different subtypes of trauma associated in schizophrenia, but only emotional neglect in bipolar disorders. However, more research is needed before we can draw clear implications from these findings.