Ade Herdian Putra, Zadrian Ardi, Ifdil, Evi Afiati, Anna Ayu Herawati
Objective : Arshad et al. (2026) reported exceptional effect sizes for a school-based positive psychology program among Pakistani adolescents in a randomized controlled trial. A critical but underexamined finding within the same dataset is the systematic, large-effect deterioration of the waitlist control group across all five measured outcomes. This commentary conducts a secondary quantitative examination of the control-group trajectory and situates it within the evidence base on waitlist-induced effect inflation. Methods : We extracted within-group repeated-measures statistics for the waitlist control group (n = 41) across three time points, quantified deterioration using Cohen’s d (pooled standard deviation) and partial eta-squared, and benchmarked between-group effect sizes against meta-analytic norms, distinguishing waitlist from care-as-usual comparators. Results : The waitlist control group deteriorated significantly across all five outcomes (partial η² = .70–.89; within-group |d| = 0.77–3.34). These trajectories inflated the apparent between-group effect sizes (Cohen’s d = 4.47–6.55) to levels 9–39 times above meta-analytic benchmarks (d ≈ 0.17–0.34). Meta-analytic evidence confirms that waitlist comparators yield larger effects (g = 0.95) than care-as-usual comparators (g = 0.63), indicating that a substantial portion of the reported effect reflects control-group decline rather than program-specific efficacy. Conclusion : Waitlist control designs in LMIC school-based research impose underappreciated risks: they may harm vulnerable participants, generate nocebo-like deterioration, and yield effect sizes incommensurable with the broader prevention literature, misdirecting policy investment away from programs with confirmed efficacy. We propose three reforms: adopting active control conditions, integrating school-based mental health professionals as embedded wellbeing monitors, and mandating deterioration-trajectory reporting. © 2026 Elsevier GmbH.
Department of Guidance and Counseling, Faculty of Education, Universitas Negeri Padang, West Sumatra, Padang, Indonesia; Department of Guidance and Counseling, Faculty of Education and Teacher Training, Universitas Sultan Ageng Tirtayasa, Banten, Serang, Indonesia; Department of Guidance and Counseling, Faculty of Education and Teacher Training, Universitas Bengkulu, Bengkulu, Indonesia
