Figure 2

Additive effects of preterm birth and maternal postpartum depressive symptoms on mental and behavioral disorders in children. The lines represent cumulative incidence rates of mental and behavioral disorders until age 8.4–12.8 years in children born at term and whose mother reported no probable clinical postpartum depression (referent), (a) in children born preterm and whose mothers reported no probable clinical postpartum depression, (b) in children born at term and whose mother reported probable clinical postpartum depression, and (c) in children born preterm and whose mother reported probable clinical postpartum depression. HR refers to hazard ratio and 95% CI to 95% Confidence Interval. Model 1 refers to unadjusted associations and Model 2 to associations adjusted for maternal age at delivery, education, smoking and/or alcohol use at any time during pregnancy, delivery mode and child sex. P value for linearity refers to the additive effect of preterm birth and maternal postpartum depression (0 = term, no postpartum depression, 1 = preterm, no postpartum depression or term, postpartum depression, 2 = preterm, postpartum depression).