Strengths and limitations
As depression during pregnancy is a strong risk factor for depression following childbirth (Nulman et al., 2012) separating out the effects of prenatal and postnatal depression on the child requires a very large sample size, which we were able to achieve. Other strengths include the use of data from a longitudinal cohort study spanning 20 years, rather than using retrospective recall of maternal depression status, and the use of validated scales to measure depression status.
Some limitations of the study should be noted. The study contained some missing data, although our imputations suggested this could not explain the findings. As with all investigations of moderation, statistical power was relatively reduced when investigating interactions between depression and gender. This highlights the importance of the large sample size and the possibilities of robust imputation which is a unique strength of this study. Other limitations inherent in a study such as this one include confounding factors which may have an impact on the development of depression in young people, such as quality of parenting, relapsing and remitting maternal depression not present at the data collection times in our study, other parental mental or physical illness, other people present in the household or influences of other caregivers, household income, and quality of education.