Effects as a function of implementation fidelity of a transdiagnostic prevention program in young school-aged children.

Super Skills for Life (SSL) is a transdiagnostic prevention program for school-aged children with internalizing problems. The current study aimed to examine the short- and long-term (12-month follow-up) effectiveness of SSL, depending on implementation fidelity. Participants were 123 Spanish-speaking children aged 6-8 years with internalizing symptoms and their parents. High (n = 41) and low fidelity (n = 26) groups were established and compared with a control group (CG) (n = 56). Compared to CG, the high-fidelity group (HFG) achieved better outcomes than the low-fidelity group (LFG) at short and long term, including symptoms of anxiety, depression, and internalizing problems, and also externalizing problems at long-term. The LFG improved key symptoms at short term (depression) and long term (anxiety and depression). Findings suggest that SSL is beneficial even if not delivered at maximum fidelity, although considering the influence of implementation fidelity is critical because the high-fidelity implementation yielded the greatest effects when compared to the CG. This research provides valuable data, analyzing for the first time the influence of fidelity on SSL outcomes in young school-aged children exhibiting internalizing symptoms, while there is still a lack of studies of these characteristics concerning transdiagnostic prevention programs targeting childhood anxiety and depression.