Why are anxiety and depressive symptoms comorbid in youth? A multi-wave, longitudinal examination of competing etiological models.

BACKGROUND The present study sought to clarify the development of comorbid emotional distress by comparing different explanations for how youth develop anxiety and depressive symptoms. Specifically, we introduced the diathesis-anxiety approach (whether cognitive vulnerabilities interact with anxiety symptoms), and compared it to a causal model (anxiety symptoms predicting depressive symptoms), and a correlated liabilities model (whether cognitive vulnerabilities interacted with stressors to predict both anxiety and depressive symptoms) to examine which model best explained the relation between depressive and anxiety symptoms in youth. METHODS 678 3rd (n=208), 6th (n=245), and 9th (n=225) grade girls (n=380) and boys (n=298) completed self-report measures at baseline assessing cognitive vulnerabilities (rumination and self-criticism), stressors, depressive and anxiety symptoms. Every 3 months over the next 18 months, youth completed follow-up measures of symptoms and stressors. RESULTS While limited support was found for a causal (p>0.10) or correlated-liability model (p>0.05) for comorbidity, findings did support a diathesis-anxiety approach for both self-criticism (t(2494)=3.36, p<0.001) and rumination (t(2505)=2.40, p<0.05). LIMITATIONS The present study׳s findings are based on self-report measure and makes inferences concerning comorbidity with a community sample. CONCLUSIONS These results may help clarify past research concerning comorbidity by introducing a diathesis-anxiety approach as a viable model to understand which youth are most at-risk for developing comorbid emotional distress.