Biological and social rhythm differences, daily melatonin secretion and psychiatric symptoms in healthy adults

Objective To examine associations of chronotype and social jetlag (SJL) with psychiatric symptoms and melatonin secretion in healthy adults.Methods In this cross-sectional study, 95 relatively young, university-affiliated students and staff completed the MEQ, SCL-90-R, MCTQ and a one-week sleep diary. SJL was defined as the workday–free-day difference in midsleep. Overnight workday urinary 6-sulfatoxymelatonin (6-SMT) was assayed by ELISA and indexed to creatinine.Results Evening chronotypes had longer SJL than intermediate and morning chronotypes (F = 16.70, p < .001). Higher MEQ scores were associated with shorter SJL and earlier midsleep (r = −0.54 to −0.66, all p < .001). Total SCL-90-R scores did not differ across chronotypes (p = .367), whereas obsessive–compulsive symptoms were higher in the evening group (p = .027). Urinary 6-SMT/creatinine did not differ by chronotype (F = 0.823, p = .442) or relate to SJL; BMI correlated inversely with 6-SMT (r = −0.21, p = .043). Lower MEQ scores independently predicted longer SJL (B = −2.82, β = −0.54, p < .001).Conclusions Eveningness was associated with greater SJL and obsessive–compulsive symptoms, whereas overnight 6-SMT was not linked to chronotype or SJL. The inverse BMI–6-SMT association may suggest metabolic relevance.