Not later, but longer: sleep, chronotype and light exposure in adolescents with remitted depression compared to healthy controls

Abstract

The relationship between sleep and adolescent depression is much discussed, but still not fully understood. One important sleep variable is self-selected sleep timing, which is also referred to as chronotype. Chronotype is mostly regulated by the circadian clock that synchronises the internal time of the body with the external light dark cycle. A late chronotype as well as a misalignment between internal time and external time such as social jetlag has been shown to be associated with depressive symptoms in adults. In this study, we investigated whether adolescents with remitted depression differ from healthy controls in terms of chronotype, social jetlag and other sleep-related variables. For this purpose, we assessed chronotype and social jetlag with the Munich ChronoType Questionnaire (MCTQ), subjective sleep quality with the Pittsburgh Sleep Quality Index (PSQI) and used continuous wrist-actimetry over 31 consecutive days to determine objective sleep timing. Given the potentially mediating effect of light on chronotype and depressive symptoms, we measured light exposure with a light sensor on the actimeter. In our sample, adolescents with remitted depression showed similar chronotypes and similar amounts of social jetlag compared to controls. However, patients with remitted depression slept significantly longer on work-free days and reported a worse subjective sleep quality than controls. Additionally, light exposure in remitted patients was significantly higher, but this finding was mediated by living in a rural environment. These findings indicate that chronotype might be modified during remission, which should be further investigated in longitudinal studies.

Health risks associated with genetic alterations in internal clock system by external factors

“…Desynchrony induced by external/environmental factors is linked with high risk of serious health issues, including depressive disorders, cardiovascular disorders, diabetes and cancer 1 , 43 . Social jet lag is associated with depressive and metabolic syndromes that further enhance the consumption of nicotine, caffeine and alcohol 3 while inappropriately timed sleep is associated with endocrine, metabolic, cardiovascular, and neurological disorders 9 . Incompatibility between circadian rhythms and working periods causes sleep deprivation 44 that further causes fatigue, vigilance and attention impairments 45 (Figure 3 ).…”

“…However, self-selected sleep and wake timing differences are possible that are linked to specific chronotypes. Opposite to the late chronotypes, early chronotypes wake up and fall asleep early in the morning and evening respectively 3 . Irregular sleeping periods and altered light-dark cycles in shift-work and long distance travel are associated with altered environment cues, which further influence daily rhythms via central and peripheral clocks 4 .…”

“…Jet lag immediately causes fatigue and indigestion while chronic exposure to jet lag has strong impacts on spatial cognition and temporal lobe 5 . Externally induced disruption in natural sleep-wake cycles 6 and circadian rhythms is associated with neuronal dysfunction 7 , 8 , increased risk for psychiatric, cardiovascular and metabolic diseases 3 , and affects bone health 9 .…”

The prognostic significance of biological rhythms assessment in depression

“…Keller и соавт. [25], сравнивая распределение хронотипов среди больных с депрессией в ремиссии и группой контроля (здоровые) отметили отсутствие статистически значимых различий, что косвенно свидетельствует о возможности его изменения (коррекции) в процессе терапии.…”

Adolescent psychiatry—from the viewpoint of a child and adolescent psychiatrist

“…Hence, adolescence is a focal point of psychiatric research and treatment. Consequently and irrespectively of the semantic circumstance that adolescence is part of this journal's name, reports both in the current issue [4,5] and numerous ones in previous issues [6][7][8][9][10][11] deal with adolescent psychiatry.…”