Smartphone app reduces psychological distress at 3 months with Cohen d -0.17Smartphone app reduces workplace stress for some workers in Japan

BACKGROUND: Although mobile health (mHealth) interventions serve as potential solutions for addressing mental health problems, evidence on whether mHealth interventions targeting physical activity can reduce psychological distress among generally healthy workers is limited. OBJECTIVE: This study aimed to investigate the effectiveness of a stand-alone smartphone app, which passively monitors physical activity and psychological distress, in reducing psychological distress among workers. METHODS: This open-label, 2-arm, parallel-group randomized clinical trial was conducted in Japan over 6 months, with assessments at baseline, 3 months, and 6 months. Eligible participants were workers aged 18 years or older who were able to complete the Japanese questionnaires and owned compatible smartphones. Individuals currently absent from work or with a history of absence due to sickness within the past 12 months were excluded. Participants were randomized (1:1) to the intervention or control group. Participants in the intervention group used a smartphone app that passively monitored physical activity and mental health for 3 months. The control group received a booklet on job stress. The primary outcome was psychological distress measured using the 6-item Kessler Psychological Distress Scale. Secondary outcomes included self-reported physical activity and digitally recorded activity duration in the intervention group. Analyses followed the intention-to-treat principle. For the main analysis, linear mixed modeling for repeated measures was used to estimate between-group differences in changes in psychological distress across the 3 time points. RESULTS: A total of 793 workers were randomized (intervention: n=397; control: n=396). Psychological distress decreased significantly in the intervention group at 3 months (mean difference -0.56, 95% CI -1.11 to -0.02; P=.04; Cohen d -0.17), although this effect was not sustained at 6 months. Self-reported physical activity levels declined in both groups without significant between-group differences. In contrast, in the intervention group, digitally recorded activity increased during the intervention period (7.92 min increase, 95% CI 1.36-14.49; P=.02); however, these data were not comparable with those in the control group. Subgroup analysis showed a larger effect among participants with no or minimal baseline distress (mean difference -0.63, 95% CI -1.16 to -0.11; P=.02; Cohen d -0.19). CONCLUSIONS: The stand-alone smartphone-based app that enables workers to monitor physical activity and psychological distress modestly reduced psychological distress among workers. However, it remains unclear whether the app reduces psychological distress through biological and psychosocial mechanisms, including increased physical activity. Furthermore, the benefit may be short-lived rather than durable and may have limited clinical and practical significance. Although mHealth interventions may contribute to preventing mental health problems in workplace settings, booster engagement strategies are necessary to sustain benefits over time. Subgroup analyses suggested that the app may be more effective among generally healthy populations.