Effectiveness of the mobile application Holidaily in reducing work-related rumination when returning to work after vacation: a randomized controlled trial

Background: Vacations reliably improve indicators of mental health, largely by providing relief from work-related stress. Low levels of work-related rumination, a key transdiagnostic factor linked to burnout and depression, are considered prerequisites for successful recovery both during vacations and in daily working life. However, such benefits are typically short-lived, with a rapid "fade-out" upon return to work. To address this challenge, we developed Holidaily, a low-threshold, gamified mobile health intervention designed to translate recovery science into daily digital practice and sustain the mental health gains of vacations. Methods: In a randomized controlled trial (RCT), Holidaily was evaluated as a digital mental health intervention targeting work-related rumination, the primary outcome. Assessments were conducted two weeks prior to vacation and two weeks after the return to work, before waitlist controls were granted access. Given the novelty of the research, a wide range of exploratory outcomes was also assessed. Results: = -0.67 (-1.0; -0.4)]. At this time, rumination levels were still reduced by 22.2% in the intervention group, compared with 6.9% in controls relative to baseline. Among app users, reductions persisted for up to four weeks (26.1%). Sensitivity analyses confirmed these results. These findings provide first evidence that a mobile health technology can extend vacation-related recovery benefits and reduce work-related rumination in workers. Conclusions: This is the first RCT to show that the rapid fade-out of vacation benefits is not inevitable. Holidaily appears to improve workers' ability to reduce levels of work-related rumination. These results highlight the potential of scalable digital interventions to foster sustainable mental health in working populations and support preventive public health efforts. Clinical Trial Registration: https://drks.de/search/de/trial/DRKS00013650, German WHO DRKS00013650.