The impact of cumulative childhood adversity on young adult mental health: measures, models, and interpretations.

Research studies investigating the impact of childhood cumulative adversity on adult mental health have proliferated in recent years. In general, little attention has been paid to the operationalization of cumulative adversity, with most studies operationalizing this as the simple sum of the number of occurrences of distinct events experienced. In addition, the possibility that the mathematical relationship of cumulative childhood adversity to some mental health dimensions may be more complex than a basic linear association has not often been considered. This study explores these issues with 2 waves of data drawn from an economically and racially diverse sample transitioning to adulthood in Boston, Massachusetts, USA. A diverse set of childhood adversities were reported in high school and 3 mental health outcomes -- depressed mood, drug use, and antisocial behavior -- were reported 2 years later during the transition to adulthood. Our results suggest that both operationalization and statistical modeling are important and interrelated and, as such, they have the potential to influence substantive interpretation of the effect of cumulative childhood adversity on adult mental health. In our data, total cumulative childhood adversity was related to depressive symptoms, drug use, and antisocial behavior in a positive curvilinear manner with incremental impact increasing as adversities accumulate, but further analysis revealed that this curvilinear effect was an artifact of the confounding of high cumulative adversity scores with the experience of more severe events. Thus, respondents with higher cumulative adversity had disproportionately poorer mental health because of the severity of the adversities they were exposed to, not the cumulative number of different types of adversities experienced. These results indicate that public health efforts targeting prevention of childhood adversities would best be aimed at the most severe adversities in order to have greatest benefit to mental health in young adulthood.