LAUSR

Social jet lag (SJL) occurs when a person’s social time (weekdays) is out of phase with their circadian time (weekend). Not much is known about the relationship between Seasonal Affective Disorder (SAD) and SJL; however, the sleep/wake cycle is very vulnerable to disruption by external factors. In a previous study in adolescents and young adults, self-reported chronotype was used to calculate SJL, and winter mood variation and SJL were found to be higher after the time change in fall and winter. Our study will directly compare SAD and non-depressed controls in the winter on SJL calculated with actigraphy in a sample of adults. Participants (N=46) ages 21-64 were recruited during winter months and included individuals with SAD (n=21) and nonseasonal, never depressed controls (n=25). Midsleep timing was measured using actigraphy (average number nights = 7), and SJL was calculated by subtracting average week midsleep from average weekend midsleep corrected for number of days. Regression analysis included diagnostic group as a predictor, age and gender as covariates, and SJL as the outcome. While the seasonally depressed group had a slightly higher average SJL (M =61.8 minutes, SD = 181.2 minutes) than the control group (M = 60.6 minutes, SD = 165 minutes; mean difference 1.2 minutes), there was no significant difference in SJL between the participants with seasonal depression and the controls (p=0.778). However, age was a significant predictor, as the younger half of the sample had a mean SJL of 94 minutes (SD=180 minutes) and the older half of the sample had a mean SJL of 24 minutes (SD= 156 minutes; mean difference= 70 minutes). There was no group*age interaction in post-hoc tests. This is the first study to test whether individuals with SAD have greater SJL than non-depressed controls, and the data do not support such a hypothesis. Results do, however, confirm prior findings that SJL decreases with age. Future studies should compare SJL in individuals with SAD during winter compared to spontaneous summer remission to test whether a change in SJL correlates with winter depression onset. NIMH K.A.R. MH103303