Mechanisms of Change in Mindfulness-Based Family Intervention (MYmind) Versus Methylphenidate for Childhood ADHD: A Randomized Controlled Trial

<b>Background/Objectives</b>: Mindfulness-based interventions show promise for treating childhood ADHD, yet the mechanisms through which they produce effects remain unclear. This study provides the first direct comparison of treatment mechanisms between a mindfulness-based family intervention (MYmind) and methylphenidate. <b>Methods:</b> Data were drawn from a preregistered trial combining randomized and preference arms, comparing MYmind (2-month parallel parent-child mindfulness training) with 4-month methylphenidate in children aged 8-18 with ADHD (N = 120 children, 224 parents). Families were assessed at baseline, 2, 4 and 10 months. Multilevel mediation analyses tested whether treatment effects on ADHD symptoms were transmitted through 111 treatment-to-mediator-to-outcome pathways across three mechanism categories: child emotion regulation and coping (all children); adolescent self-regulation and mindfulness (ages 11+); and parent-level mechanisms, including mindful parenting, parental mindfulness, parenting style and self-compassion. <b>Results:</b> Direct treatment effects favored methylphenidate for ADHD symptom reduction at 4 months, with mindfulness catching up by 10 months. MYmind produced significantly greater improvements than methylphenidate in adolescent healthy self-regulation, parental self-compassion, mindful parenting and over-reactive parenting. Treatment did not differentially affect the remaining mechanisms. Across model sets, observed emotion regulation, maladaptive coping, parental self-compassion and mindful parenting each predicted ADHD outcomes. Across 111 pathways tested in 18 models, numerous significant individual pathways were consistent with theoretical predictions, yet no complete mediation chains reached statistical significance. <b>Conclusions:</b> MYmind engages distinct psychological and family-level processes compared to methylphenidate that are separately associated with ADHD symptom improvement. The absence of significant mediation effects likely reflects power limitations. These findings support mindfulness-based family intervention as a viable alternative to medication and highlight the need for larger-scale mechanism research.