Moderators and mediators of outcomes of parents with substance use problems: further evaluation of the Parents under Pressure programme

Background and aims Family‐focused interventions can improve family functioning when parents have substance use problems. However, there has been little focus upon potential predictors of change and analysis of mechanisms of change. This study aims to identify mediators and moderators of change in a pragmatic, multi‐site, randomized controlled trial of the Parents under Pressure (PuP) programme, a family‐focused intervention for parents with substance use and other problems, and treatment‐as‐usual (TAU). Design Secondary analysis of data: multi‐level modelling was used to investigate moderators of treatment outcome; mediation was tested with cross‐lagged models. Setting Community‐based family support services in the United Kingdom. Participants Parents (n = 100) attending community‐based addiction services with children aged 2.5 years or younger. Measurements Predictors of the primary outcome, child abuse potential, were: baseline child age and gender, composite family risk score, parental substance use and parental emotional dysregulation. Mediation was tested across three time‐points with the observed variables parental emotion dysregulation and child abuse potential. Findings Increased child age [Z = 2.14, 95% confidence interval (CI) = 0.01, 0.33] at baseline was associated with greater reductions in child abuse potential for PuP programme participants compared with TAU. Poorer parental emotional regulation (Z = 2.48, 95% CI = –2.76, −0.32) was associated with greater reductions in child abuse potential for all participants. Parental substance use (either recent use or primary substance of concern) did not alter any treatment effects on child abuse potential. The mediation analysis showed that PuP produced greater improvements in emotional regulation at post‐treatment (P