Background. Social rhythm disruption life events are significant predictors of mood relapse in bipolar patients. However, no research has examined the relationship between these events and their hypothesized mechanism of action: disrupted sleep-wake patterns. The goal of this study was to test whether participants with major depressive disorder have a greater disruption of daily sleep and motor activity following disrupting life events when compared to normal controls.

Method. Over the course of 2 weeks, 39 normal controls and 39 individuals with major depressive disorder completed life events interviews and wore actigraphs to obtain estimates of sleep/wake activity.

Results. Statistically significant interactions indicated that the presence of at least one disrupting life event in the previous 4 months correlated with elevations in the amount of time spent awake after sleep onset [β=0·45, ΔF(1,73)=4·80, p<0·05], and decreases in the percentage of time spent asleep [β=−0·53, ΔF(1,73)=6·57, p<0·05], in depressed individuals but not in normal controls.

Conclusions. The results indicated that depressed individuals may be more susceptible to the effects of life events on sleep than normal controls. This is the first study to date to correlate life events with objective measures of sleep. However, prospective longitudinal research is necessary to clarify the temporal relationship among these variables.