Circadian rhythm and insomnia in youths

Abstract

The current thesis aimed to examine the interplay between circadian rhythm and insomnia in the context of youth mental health.

Study 1 was a systematic review and meta-analysis that examined the association between evening preference and mental health outcomes in youths. Eighty-one observational studies were included in the review. Eveningness was found to be significantly associated with general psychopathologies (r = 0.20), mood-related disturbances (r = 0.17), and anxiety problems (r = 0.15). Qualitative review also identified that eveningness was associated with greater risks for psychotic symptoms and maladaptive eating behaviours. These findings highlighted the need to consider circadian preference in assessing and managing psychopathologies in youths.

Study 2 validated the Chinese version of the Munich Chronotype Questionnaire (MCTQHK), a self-report measure to assess the time of sleep-wake behaviour, in a sample of local youths and explored its utility in individuals with insomnia. A total of 659 youths aged 15-24 completed a series of subjective and objective circadian measures. The MCTQHK midpoint of sleep was significantly correlated with multiple circadian parameters (|r| = 0.36 to 0.65). The study demonstrated that MCTQHK is suitable for assessing chronotype with good reliability and validity in Chinese youths and provided preliminary support for its utility in individuals with insomnia.

Study 3 was a case-control study that compared the circadian characteristics of youths with DSM-5 insomnia disorder (n = 70) and delayed sleep-wake phase disorder (n = 34), as well as healthy sleepers (n = 35). Participants completed actigraphy monitoring and dim-light melatonin onset assessment (DLMO). The results showed that the insomnia group had a later endogenous melatonin phase and shorter DLMO to habitual bedtime phase angle than healthy sleepers. Furthermore, short phase angle was significantly associated with increased sleep onset latency in youths with insomnia disorder. The findings suggested that a spectrum of circadian factors might be implicated in the pathophysiology of youth insomnia.

Study 4 explored the subtypes of youth insomnia using latent profile analysis. Three subtypes with distinct characteristics (i.e., insomnia with short sleep, insomnia related to circadian factors, and insomnia related to cognitive and behavioural factors) were identified from 104 youths with chronic insomnia symptoms. The preliminary findings on these insomnia subtypes might provide a basis for planning individualised treatment strategies in future clinical management of youth insomnia.

Study 5 was a randomised controlled trial that examined the efficacy of cognitive behavioural therapy for insomnia (CBT-I) with (CBTI+BLT) or without adjunctive bright light therapy (CBTI-BLT) in youths with sleep-onset insomnia and eveningness. A total of 114 participants were randomly allocated to one of the groups: CBTI+BLT (n = 38), CBTI-BLT (n = 37), and waitlist control (WL; n = 39). Both intervention groups significantly improved insomnia severity and clinician-rated mood symptoms at post-treatment and 1-month follow-up relative to WL. Only the CBTI+BLT significantly advanced the circadian phase at post-treatment. The results supported adjunctive BLT in addressing the circadian factors in youth insomnia.

In conclusion, the present thesis demonstrated the crucial roles of circadian factors in the pathophysiology of youth insomnia. Enhanced attention to circadian issues is warranted in the clinical management of youth insomnia.