According to Lewisohn’s model of depression, decreases in behavioral activation (BA) occurring after facing a vital stressor may increase the risk of depression. Transition to parenthood is a potentially stressful life event that increases the risks of postpartum depression. We aimed to (1) describe the changes in BA and depressive symptomatology between the prepartum period, one month, three months, and six months postpartum and (2) evaluate the bi-directionality of the relationship between intraindividual changes in BA and intraindividual changes in depressive symptoms longitudinally. Method: Chilean pregnant women (N = 503) completed a battery of questionnaires when they were between 32 and 37 weeks of gestation, and one, three, and six months after delivery. Results: A repeated measures ANOVA showed that BA significantly decreased from the prepartum to one month postpartum. A Random Intercept Cross-lagged Panel Model (RI-CLPM) supported the bidirectional inverse relationship between intraindividual changes in BA and intraindividual changes in depressive symptoms. The effect sizes of these associations were large (ßs ranging from -.141 to -.243) according to Orth et al. (2022)’s recommendations for cross-lagged effect benchmarks. This relationship showed robustness when multi-group RI-CLPMs were conducted to adjust for several covariates (i.e., marital status, the type of health insurance, type of delivery, primiparous versus multiparous participants, and pregnancy or delivery complication or newborn health problem). Nonetheless, reporting a previous history of major depression moderated this relationship so that intra-individual decreases in BA more likely led to intra-individual increases in depressive symptoms in people with a history of depression than in people without such a history. We discuss implications for behavioral models of depression.
