LAUSR

The early postpartum is a time of expected maternal sleep loss, normalized as part of infant care. While short duration and disrupted nocturnal sleep are posited risk factors for postpartum depression (PPD), the role of daytime sleep remains less understood, despite the widespread recommendation that mothers sleep when their baby is sleeping. This study examined associations between napping, stress, and longitudinal PPD in a sample of in a sample of healthy first-time mothers, using a prospective ambulatory field study design. Fifty primiparous women (62% non-White; mean age=32 years) without a history of sleep disorders or psychopathology completed 10-days (9-nights) of actigraphy and sleep diaries at postpartum week 6. Sleep variables included nighttime duration and efficiency, and daytime nap frequency, timing and duration. Participants completed 3-days of superimposed ecological momentary assessment (EMA) rating naturalistic infant-related stressors (task demand; effort-reward-imbalance) at four daily intervals. Hierarchical mixed models tested whether daytime sleep characteristics predicted lower depression levels (via Edinburgh Postnatal-Depression Scale - EPDS) at 6-weeks, 8-weeks, and 3-months postpartum. Time-varying within-person covariates included time-of-day, baseline depression and anxiety (via Generalized-Anxiety-Disorder-7 scores), and previous night sleep. To test the putative stress-protective role of napping, we examined pre-post nap differences in EMA ratings. Sixty percent (n = 30/47) of women napped regularly (>3x/1 week, between 1-5 PM, < 90 min by both diary and actigraphy), rating 80% of these naps “intentional.” Women with greater nap regularity at 6-weeks had lower depression levels at all timepoints (Betas = -2.4(1.6); -1.4(.5), -.5(.01) ps<.001, respectively), and less of an increase in depression symptoms at 3-months postpartum, compared to non-nappers [Beta(SE)=-1.2 (.5); R^2=.21; p<.001]. At 6-weeks, regular nappers reported lower stress post-nap (effort-reward-imbalance; demand) [Beta(SE)=-6.3(1.4); 1.2(.12,), R^2=.27, .32, respectively; ps<.01]. This study demonstrates a contemporaneous mood-protective role of daytime sleep in a perinatal sample, using 24-hr objective sleep assessment coupled with daily assessments of naturalistic stressors. Moreover, these results provide support for the protective role of regular daytime sleep on development of PPD over time. Among new mothers who regularly nap, lowered post-nap stress may be one pathway through which daytime sleep buffers against PPD severity. NIMH-1R36MH118000-01, CTSI89431, T32-HL007713