Syndrome co-occurrence and treatment outcomes in youth mental health clinics.

Despite widespread speculation that syndrome co-occurrence undermines treatment outcomes, this hypothesis has not been fully examined within clinical care settings. To address this gap, the authors investigated the relation between syndrome co-occurrence and outcome among 325 clinically referred youths. For every syndrome, higher initial severity was predictive of greater treatment gains and higher posttreatment symptom levels; contrary to speculation in the literature, co-occurrence effects were rare and modest in size, accounting for 0.6% of outcome variance on average. The results suggest that co-occurrence, though common in youth clinical care, is not an obstacle to treatment success in most cases. In addition to its substantive findings, the study illustrates how a dimensional approach can be used to shed new light on co-occurrence in clinical care.