Joint Effects of Indoor Air Pollution and Maternal Psychosocial Stress During Pregnancy on Trajectories of Early Childhood Psychopathology

Background and aim: Identifying modifiable risk factors for childhood psychopathology can increase quality of life for children and prevent adult psychopathology. Previous studies have shown that indoor air pollution (IAP) and maternal psychosocial stress (MPS) during pregnancy separately influence psychopathology, but their joint effects are not well understood. Here, we use environmental mixture methodology to estimate joint effects of IAP and MPS during pregnancy on trajectories of early childhood psychopathology. Methods: We used data from the Drakenstein Child Health Study (N=360), a South African birth cohort. Exposure to IAP and MPS was measured during the second trimester of pregnancy. The Childhood Behavior Checklist (CBCL) was administered at ages 2, 3.5, and 5 years to assess child psychopathology. CBCL trajectories were created using latent class linear mixed effects models. Joint effects of IAP and MPS were summarized using principal component (PC) analysis. Individual effects of IAP and MPS and their joint effects were estimated using polytomous logistic regression models, adjusted for maternal age, sex, ancestry, and socioeconomic status. Results: Three distinct classes of CBCL trajectory were identified (class 1 (reference): lowest, class 2: highest and increases, class 3: stable at a medium-high). We consistently observed adverse associations between IAP (e.g., toluene for class 3: OR [95% CI]; 1.35 [1.00, 1.80]) and MPS (e.g., intimate partner violence for class 3: 1.44 [1.03, 1.99)) and CBCL. In the joint effects analysis, PC2 (accounted for 13% of risk factor variation) was significantly associated with class 3 (1.23 [1.03, 1.46]) and class 2 (1.27 [1.04, 1.55]) compared to class 1. Conclusions: Exposure to IAP and MPS during pregnancy was associated with CBCL trajectories indicating increased risk for psychopathology. Estimating joint effects of IAP and MPS is important to identify vulnerable subgroups for intervention to prevent childhood psychopathology. Keywords: indoor air pollution, psychopathology, exposure mixtures