Chronotype and its relationship to sleep quality in patients with affective disorders and co-occurring insomnia

Introduction: Poor sleep is common in depression, has been shown to precede acute episodes, and persists during remission. Circadian abnormalities are involved in the pathogenesis of depression and are one of the prominent factors underlying sleep disturbances. Therefore, we studied the relation between circadian preferences (chronotype) and sleep quality in patients with affective disorders accompanied by clinically relevant insomnia. Methods: Forty-eight inpatients (29 f/19 m; age: 42.5 ± 14.2 years) with mainly depressive disorders (ICD-10: F32/33) and co-occurring insomnia complaints (Pittsburgh Sleep Questionnaire Index, PSQI global sore ≥ 5) completed the Morningness-Eveningness Questionnaire (MEQ) and the Beck Depression Inventory-II (BDI). Results: Patients were classified as 12 evening types, 25 intermediate types, and 11 morning types. Chronotypes did not differ in BDI-II, but substantial age differences were found: evening types were younger than intermediate types (p < 0.05) and morning types (p < 0.01). When compared with evening types or intermediate types, morning types showed a shorter sleep duration as assessed by the PSQI (each p < 0.05). Correlation analyses revealed a positive relationship between MEQ scores and the PSQI subscale sleep efficiency (the higher the MEQ score towards morningness, the lower the sleep efficiency) (p < 0.05), although this association was found to be mediated by age. Evening types exhibited a tendency towards a longer sleep latency (p < 0.1).