Are punitive parenting and stressful life events environmental risk factors for obsessive-compulsive symptoms in youth? A longitudinal twin study.

Background
Punitive parenting and stressful life events are associated with obsessive-compulsive symptoms (OCS). However, the lack of longitudinal, genetically-informative studies means it remains unclear whether these factors represent environmentally-mediated risks for the development of OCS.

Methods
Twins and siblings from the Genesis1219 study completed self-report questionnaires two years apart (Time 1: N = 2616, mean age = 15.0; Time 2: N = 1579, mean age = 17.0 years) assessing OCS, maternal and paternal punitive parenting, and dependent stressful life events. Multiple regression models tested cross-sectional and longitudinal associations between the putative environmental risk factors and obsessive-compulsive symptoms using: (a) individual scores; and (b) monozygotic twin difference scores. The aetiologies of significant phenotypic associations between putative risk factors and OCS were further examined using multivariate genetic models.

Results
At a phenotypic level, maternal and paternal punitive parenting and stressful life events were all associated with OCS both cross-sectionally and longitudinally. However, only stressful life events predicted the subsequent development of OCS, after controlling for earlier symptoms. Genetic models indicated that the association between life events and change in OCS symptoms was due to both genetic (48%) and environmental (52%) influences. Overall, life events associated with change in OCS accounted for 1.2% of variation in OCS at Time 2.

Conclusions
Stressful life events, but not punitive parenting, predict OCS change during adolescence at a phenotypic level. This association exists above and beyond genetic confounding, consistent with the hypothesis that stressful life events play a causal role in the development of obsessive-compulsive symptoms.