BackgroundIt is not known whether associations between child problem behaviours and maternal depression can be accounted for by comorbid borderline personality disorder (BPD) dysfunction.AimTo examine the contributions of maternal depression and BPD symptoms to child problem behaviours.MethodDepression trajectories over the fist-year postpartum were generated using repeated measurement from a general population sample of 997 mothers recruited in pregnancy. In a stratified subsample of 251, maternal depression and BPD symptoms were examined as predictors of child problem behaviours at 2.5 years.ResultsChild problem behaviours were predicted by a high maternal depression trajectory prior to the inclusion of BPD symptoms. This association was no longer significant after the introduction of BPD symptoms.ConclusionsRisks for child problem behaviours currently attributed to maternal depression may arise from more persistent and pervasive difficulties found in borderline personality dysfunction.