Clinical Associations of Chronotypes in Adolescents and Young Adults with Mental Disorders

Abstract

Youth represents a sensitive period for the onset of both circadian disturbances and mental disorders. There are some suggestions that circadian disturbances may be an early feature or may directly contribute to the emergence, perpetuation, and recurrence of some mental disorders, particularly affective disorders. A person’s ‘chronotype’ characterises their circadian preferences for early or late bed and wake times and their peak cognitive and physical activities across the 24-hour period. In this thesis, the chronotype of young persons with various mental disorders is examined. Study 1 evaluated chronotypes, as assessed with the Horne-Östberg questionnaire, in young people with emerging anxiety, depression, bipolar, or psychotic disorders and healthy controls. Associations between Morningness-Eveningness preference and the severity of various psychiatric symptoms were assessed. Four hundred and ninety-six individuals aged 12-30 years (mean age + SD: 19.5 + 4.2) were divided according to primary diagnosis and were assessed with the Social and Occupational Functioning Scale (SOFAS), the Hamilton Depression Rating Scale (HDRS), the Brief Psychiatric Rating Scale (BPRS), the Kessler Psychological Distress Scale (K10) and the Horne-Östberg Morningness-Eveningness questionnaire (ME). A significant diagnostic group effect was found for the ME (ANOVA: F (4, 491) = 9.1, p < 0.001) and remained significant after controlling for age and gender (ANCOVA: F (4, 489) = 8.2, p < 0.001). Post hoc tests showed that the anxiety (p < 0.001), depression (p < 0.001), bipolar (p < 0.001) and psychosis (p = 0.045) groups had significantly lower ME scores (i.e. higher eveningness) compared to the control group. Significant negative correlations were found between clinical scales (i.e. HDRS, BPRS, SOFAS, K10) and ME for all diagnostic groups, suggesting that participants with more pronounced eveningness had worse symptom severity than those with more pronounced morningness. 8 Study 2 examined temporal variations in chronotypes and investigated longitudinal associations between changes in Morningness-Eveningness preference and changes in symptom profiles in 133 young people (12-35 years) with primary depression or bipolar disorder. From a categorical perspective, 33% of all participants shifted to a later chronotype from baseline to follow-up (F (1, 105) = 7.5, p = 0.007). After controlling for age, gender and longitudinal period length, significant interactions showed that participants who shifted to earlier chronotypes showed more prominent longitudinal improvements in depressive (F (1, 108) = 4.6, p = 0.035) and negative (F (1, 115) = 6.6, p = 0.011) symptoms on the BPRS than participants who remained in the same chronotype category or shifted to later chronotypes. The results obtained from these studies suggest that many young persons with emerging mental disorders present with a strong eveningness preference, which is in turn associated with worse clinical profiles. Longitudinally, those persons with depression or bipolar disorder who shift towards more morningness also showed the strongest clinical improvements. Overall, these findings suggest that evening chronotypes are associated with worse psychiatric symptom severity and highly likely to be reflective of state changes across the course of mental illnesses. These findings have implications for clinical practice in young persons with emerging mental disorders. Morningness-Eveningness preference is unlikely to be a static trait in the context of youth and mental disorders. Treatment strategies targeting the circadian system are highly likely to be relevant for patients presenting with affective disorders and late chronotypes.