Purpose <p>Maternal depression is associated with mental health difficulties in children, but it is unclear how the timing or duration of depressive symptoms impact child outcomes. This study tested three life course frameworks in the longitudinal association between maternal depression and child mental health: sensitive periods, accumulation, and chain of risk.</p> Methods <p>841 mother-child dyads in Pakistan were followed from pregnancy through child age 7. Maternal depressive symptoms were assessed during the third trimester of pregnancy, infancy (3 and 6 months postpartum), early childhood (child age 2 and 3), and middle childhood (child age 4 and 6). Child mental health difficulties were measured at age 7. Path modeling was used to test each life course hypothesis.</p> Results <p>Maternal depressive symptoms during early childhood and middle childhood, but not pregnancy or infancy, were associated with increased mental health difficulties at child age 7. Results supported the accumulation model, meaning there was a dose-response relationship between the number of periods of maternal depression and child mental health difficulties. Results also supported a chain of risk model, suggesting that early maternal depression can trigger a cascade of intervening maternal depressive episodes, the most recent of which are associated with child mental health.</p> Conclusion <p>Results show that early exposure to maternal depression impacts children’s later mental health through subsequent exposure to maternal depression. In addition, recent exposure to maternal depression is particularly impactful for child mental health. This suggests that interventions for maternal depression may benefit children at multiple points in the life course.</p>