Effectiveness of a Participatory Voice Intervention on Psychological Well-Being Among Warehouse Workers: Results From the Fulfillment Center Intervention Study, United States, 2021‒2023.

<b>Objectives.</b> To examine whether a novel workplace intervention designed to increase worker voice can reduce psychological distress and improve emotional vitality at 6- and 12-month follow-up. <b>Methods.</b> We conducted a cluster-randomized controlled trial in 16 fulfillment centers throughout the United States between 2021 and 2023. Data were collected at 3 time points; 2813 workers participated in at least 1 survey. Treated fulfillment centers established a new, participatory committee called the Health and Well-Being Committee. We compared differences in psychological distress and emotional vitality and explored differential treatment effects by gender. <b>Results.</b> At baseline, 51% of the participants reported moderate or severe psychological distress. Intervention sites had lower average psychological distress at the 6-month follow-up compared with control sites, with no significant differences at 12-month follow-up. Gender moderation analyses suggest the Health and Well-Being Committee was particularly effective in reducing psychological distress among men at 6-month follow-up. <b>Conclusions.</b> Our findings suggest that opportunities for workers to share concerns with a committee of their peers tasked with identifying solutions can support mental health. Our study contributes important experimental evidence on workplace interventions that improve the well-being of low-wage US populations. <b>Trial Registration.</b> Clinicaltrials.gov identifier: NCT05199415. (<i>Am J Public Health.</i> 2026;116(4):522-532. https://doi.org/10.2105/AJPH.2025.308352).