Abstract
Enhancing the well-being of mentally healthy workers (i.e., those with lower psychological distress) is important to prevent mental health conditions, aligning with the trend of occupational positive psychology. No intervention study has investigated the effect of digital health intervention on well-being among workers with low levels of psychological distress in micro- and small-sized enterprises (MSEs). This secondary analysis examined the effectiveness of a fully automated text-based stress management program, "WellBe-LINE," using the LINE app to improve the well-being of employees with low levels of psychological distress in MSEs. It used data from a previous randomized controlled trial (RCT) study. The previous RCT recruited adult Japanese full-time employees at an enterprise with fewer than 50 employees from registered members of a web survey company. From the RCT, only participants with low psychological distress (Kessler 6 score under 4) were employed for the present analyses. Participants in an intervention group received text messages once per week for 8 weeks. Well-being was assessed by the Mental Health Continuum-Short Form (MHC-SF) at baseline, post (2-month), and follow-up (6-month) surveys. A mixed model for repeated measures conditional growth model analysis was conducted using a group*time interaction as an intervention effect. 638 (62.5%) participants with low psychological distress were included in this secondary analysis from the 1,021 total participants. The intervention group showed a significant intervention effect post survey on improving well-being (Cohen's d = 0.19 [95%CI 0.03-0.35], p = 0.016) and social well-being at both the post and follow-up survey with a small effect size (Cohen's d = 0.26 [95%CI: 0.10-0.42], d = 0.17 [0.002-0.34]; respectively). No effect was observed on emotional and psychological well-being. This study suggested that fully automated universal mental health interventions with low intensity may benefit the healthy population. Further research is needed, focusing on the development and evaluation of programs aimed at promoting well-being and positive mental health among mentally healthy workers as part of primary mental health prevention.Trial registration: The study protocol was registered in the UMIN clinical trial registration before starting recruitments: UMIN000050624 (registration date: March 18, 2023) https://center6.umin.ac.jp/cgi-bin/ctr/ctr_view_reg.cgi?recptno=R000057552 .