PURPOSE OF THE RESEARCH:Burgeoning evidence that modifiable parental factors can influence children's and adolescents' risk for depression and anxiety indicates that parents can play a crucial role in prevention of these disorders in their children. However, it remains unclear whether preventive interventions that are directed primarily at the parent (i.e. where the parent receives more than half of the intervention) are effective in reducing child internalizing (including both depression and anxiety) problems in the longer term. PRINCIPAL RESULTS:Compared to a range of comparison conditions, parenting interventions reduced child internalizing problems, at a minimum of 6months after the intervention was delivered. Mean effects were very small for measures of internalizing and depressive symptoms, and small for measures of anxiety symptoms. Pooled effects for anxiety diagnoses were significant and indicated a number needed to treat (NNT) of 10. Pooled effects for depression diagnoses approached significance but suggested a NNT of 11. These results were based on effects reported at the longest follow-up interval for each included study, which ranged from 6months up to 15years for internalizing measures, 5.5years for depressive measures, and 11years for anxiety measures. MAJOR CONCLUSIONS:Our findings underscore the likely benefits of increasing parental involvement in preventing internalizing problems, particularly anxiety problems, in young people.