Prevalence of self-reported postpartum depression specific to season and latitude of birth: evaluating the PRAMS data.

To determine whether season of infant birth or amount of daylight at time and location of birth is a risk factor for self-reported postpartum depression (PPD). The primary hypothesis was that the prevalence of PPD will peak during the darkest winter months. A cross-sectional analysis was conducted using the Pregnancy Risk Assessment Monitoring System (PRAMS) Phase 5 (2004-2006) data set (N = 67,079). Self-reported PPD was established using a modified version of the Patient Health Questionnaire-2 (PHQ-2) included in the PRAMS questionnaire. Logistic regression for complex survey design was used to determine odds ratios and 95% confidence intervals. No significant relationship was found between mild or moderate PPD and either season of birth or length of daylight at birth. By analyzing a large, multi-state sample, this study adds to the equivocal preexisting literature suggesting that there is no significant relationship between the season of birth or length of daylight at birth and PPD.