Children with Elevated Psychosocial Risk Load Benefit Most from a Family-Based Preventive Intervention: Exploratory Differential Analyses from the German "Strengthening Families Program 10-14" Adaptation Trial

While the effectiveness of substance use prevention programs such as the Strengthening Families Program 10-14 (SFP) has been demonstrated in the USA, European SFP adaptations have not replicated these sizable effects. Following the rationale of the risk moderation hypothesis positing that elevated risk groups may benefit more from a preventive intervention than lower-risk groups, we reanalyzed evaluation data from a randomized controlled trial testing the adapted German version of SFP (SFP-D). We hypothesized a differential impact of risk status on intervention results. The study employed a minimal control condition. Of the N = 292 participating children, 73.5% qualified as at-risk because they lived in a deprived urban district, and 26.5% qualified as high risk because they additionally scored as "difficult" in the German Strengths and Difficulty Questionnaire (parents' reports using gender- and age-specific German norms). Outcomes were children's self-reports on substance use, mental health, family functioning, and quality of life. Data were analyzed with repeated measures linear mixed models and relative risk analyses. The high-risk group in the SFP-D condition achieved the best results compared with all other groups, especially in mental health and quality of life. Relative risk analyses on tobacco [alcohol] abstinence showed that an additional percentage of 29.8% [16.0%] of high-risk children in nonabstinent controls would have remained abstinent if they had participated in SFP-D. We conclude that risk load influences the impact of substance use prevention programs and discuss to what extent differential analyses can add value to prevention research.