We recognize several limitations in our analyses. Although we employ the most commonly used measure of depressive symptomatology, we acknowledge that including a clinical diagnosis of antenatal and PPD would have increased the value of our findings. Also, misclassification bias may arise when relying on self-report methods to assess breastfeeding outcomes. Thirdly, even though we use a large population-based sample with low loss to follow-up, sampling bias resulting from the voluntary nature of participation in the survey could have influenced results. For instance, we acknowledge a shortfall in the numbers of ethnic minority mothers that may limit the generalizability of the results. Finally, even though we control for many more potential confounders than any other study on the subject, there may remain some unobserved factor, for example aspects of maternal IQ or personality, which could affect the results.