Effectiveness of a Mobile-Based Self-Regulation Training on Youths’ Affect

<b>Background:</b> The rising prevalence and enduring impact of mental health problems in youth have intensified the call for population-level prevention. Low positive and high negative affect in childhood are vulnerability factors for mental health problems in adolescence. Supporting youth in managing affect during early adolescence may foster mental health preventively. Self-regulation training has shown promise in this regard. Moreover, its parallels with Behavioral Activation (BA) align with the recommendation to adapt evidence-based clinical interventions into scalable, accessible formats for prevention. <b>Methods:</b> This study examined whether a 12-day mobile-based self-regulation training, consistent with BA principles and delivered in an innovative digital format, could increase positive and decrease negative affect in a sample of 156 youths (<i>M_age</i> = 10.0). <b>Results:</b> No significant group differences emerged in affect change over time, and neither baseline levels of self-control nor emotion regulation strategies moderated the effects. <b>Conclusions:</b> The findings suggest that low-intensity mobile-based interventions may be insufficient to produce meaningful affect change in youth. The potential need to shift from universal prevention strategies to more selective approaches targeting at-risk youth is discussed.