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This study explores the correlation between heat exposure and perinatal depression in four low- and middle-income countries using a spatial, time-stratified case-crossover study. Cluster-level mental health data from the Demographic and Health Surveys (DHS) of Bangladesh, Lesotho, Mozambique, and Nepal was utilized. Availability of complete data on Patient Health Questionnaire 9 (PHQ-9) was an inclusion criterion. Heat exposure data was provided by the National Aeronautics and Space Administration (NASA). Spatial alignment between DHS clusters and meteorological points was achieved using bilinear interpolation. Heat exposure was defined as the daily maximum temperature exceeding the country-specific 50th percentile.

This study included 1836 perinatal women with depression. The pooled prevalence of perinatal depression was 27% (range: 19%–31%). Using distributed lag non-linear model (DLNM), in Bangladesh, lower maximum ambient temperatures (25th-centile) had 5.34 (4.28, 6.66) times higher cumulative odds for perinatal depression compared to the median temperature. In Lesotho, Mozambique, and Nepal, exposure to higher maximum ambient temperature (75th centile) had cumulative higher odds of 1.19 (0.98, 1.43), 2.51 (1.96, 3.20), and 9.41 (4.88, 18.1), respectively, in comparison to the median temperatures.The results suggest that heat exposure is correlated with perinatal depression, undermining the need for intersectoral responses that address environmental and healthcare system factors.