stress-related psychiatric conditions, the present findings about the importance of longitudinal phenotypes will need to be evaluated in other ethnic groups. Second, the assessment of depression relied on four noncontiguous one-year assessment windows. Thus some recurrent cases might have been misclassified as single-episode depression, because additional depressive episodes occurred outside the assessment windows. This misclassification may have decreased the effect size of the difference between persistent and single-episode groups. However, cases classified as persistent are unlikely to be misclassified and therefore, this limitation does not invalidate our results on persistent depression. The non-contiguous assessment windows also mean that despite constructing longitudinal phenotypes of depression, we were not able to distinguish between chronic and recurrent depression. Therefore the term ‘persistent depression’ is used in accordance with current terminology (Young et al., 2008). Third, childhood maltreatment was assessed by different instruments in each cohort. Objective indicators and interview measures of adversity have generally produced more consistent results and are less affected by reporting style and recall bias than self-report questionnaire (Karg et al., 2011; Monroe, 2008; Uher and McGuffin, 2010). This may explain why the results in the Dunedin cohort, which used a combination of observer ratings and interview, were statistically somewhat
