Relation between morningness–eveningness score and depressive symptoms among patients with delayed sleep phase syndrome

ObjectivesDepressive symptoms are observed in a relatively large series of patients with delayed sleep phase syndrome (DSPS). This study was undertaken to investigate the prevalence, characteristics, and factors associated with depressive symptoms among DSPS patients.MethodsThis study targeted 90 consecutive patients (54 men, 27.1 ± 9.2 years old) diagnosed as having DSPS. Demographic and clinical characteristics were assessed at their initial visit, including application of the Zung self-rating depression scale (SDS) and morningness–eveningness questionnaire. A series of logistic regression analyses were conducted to determine the factors associated with depressive symptoms (determined as SDS ⩾ 48).ResultsSixty-four percent of the DSPS patients were in a moderate or severe depressive state. Diurnal variation, sleep disturbance, fatigue, and psychomotor retardation were the main depressive symptom items on SDS in the DSPS patients. Logistic regression analyses showed that SDS ⩾ 48 was significantly associated with moderate and definite evening chronotype. In contrast, self-reported nocturnal sleep onset and offset times were not associated with depressive symptoms.ConclusionsThere is a high prevalence of depressive symptoms among the DSPS patients. The symptomatic structure of depressive symptoms in this population appears to differ from those of typical depression. Moreover, results of our study suggest that depressive symptoms are more associated with the preference of the evening chronotype rather than sleep–wake phase among DSPS patients.