The prospective impact of sleep duration on depression and mania

OBJECTIVE: Many patients report sleeping less than 6 h per night during episodes of depression and mania. This type of sleep deficit may also be a risk factor for subsequent mood episodes; however, the long-term impact of sleep deficit remains unclear. The current study is among few longitudinal studies to assess the prospective effect of sleep deficit on depression and mania. METHODS: A subsample of 54 individuals from a longitudinal study of bipolar I disorder was selected. Participants entered the study during a mood episode. Baseline symptom data were collected at month 4 to allow for recovery from the initial episode, sleep was assessed at month 6, and follow-up symptom data were obtained during months 7-12. RESULTS: Sleep deficit predicted depressive symptoms across the 6-month follow-up but not mania. CONCLUSIONS: It is likely that the impact of sleep deficit on mania was probably missed because assessments covered a full month. Monitoring sleep duration may help predict depression in bipolar disorder and provide an opportunity for targeting intervention.