Beyond Linear Risk: A Machine Learning Approach to Understanding Perinatal Depression in Context.

The goal of this study was to investigate the contextual nature of prenatal depression (PND) and postpartum depression (PPD). We report an investigation of maternal PND and PPD using nonrandomly clustered data from 8,936 mothers in 16 cohorts in the Environmental influences on Child Health Outcomes (ECHO) Cohort. We used a recursive partitioning algorithm (ctree) to account for differential effects arising from predictor and effect heterogeneity across cohort to identify contexts, and the characteristics comprising these contexts, associated with PND and PPD. Consistent with Bronfenbrenner's bioecological systems framework, risk factors for PND and PPD are heterogeneously and synergistically present in context: the same variables did not consistently present as risk factors across groups. Findings from this study support the idea that the presence or absence of medical (and sociodemographic) risks do not have simple associations with perinatal depression. To that end, no univariate predictors of PND and PPD can be said to constitute risk absent the broader context of mothers' lives. Thus, a more useful research question than "which variables increase risk for PPD?" is "in what contexts, or in which subgroups, does a particular risk or set of risks contribute to perinatal depression?"