Selective Prevention of Depression in Stressed Workers Using a Smartphone App: A Randomized Controlled Trial (Preprint)

BACKGROUND Workplace stress is a risk factor for depression, but few interventions exist to prevent depression among stressed workers. OBJECTIVE This trial aimed to evaluate the efficacy of a smartphone-based intervention to reduce depression onset and improve related outcomes in stressed workers. METHODS A randomized controlled trial was conducted with employed participants who reported no clinically significant depression and at least moderate stress. The intervention group (n=1,053) used Anchored, a self-directed smartphone app-based cognitive behavioural and mindfulness intervention. The attention-control group (n=1,031) used a psychoeducation website. Assessment occurred via online self-report questionnaires at baseline and 30 days, 3 months, and 6 months post-baseline. The primary outcome was new depression caseness aggregated over the follow-up period. RESULTS There was no significant between-group difference in new depression caseness (z=0.69, P=.49), however those in the Anchored arm had significantly greater symptom reduction at 30 days (P=.049) and 6 months (P=.03). Notably, for Anchored participants completing at least two thirds of the intervention, there was a significantly lower rate of depression onset (1.1%, 95% CI 0.0%–3.7%) compared to controls (9.0%, 95% CI 6.8%–12.3%) at post-intervention (z=4.50, P<.001). Significant small-to-medium effect sizes for most secondary outcomes were seen in these highly engaged Anchored users compared to controls, with effects maintained at 6-month follow-up. CONCLUSIONS Amongst stressed workers, Anchored was associated with a small comparative reduction in depressive symptoms compared to controls, though selective prevention of case-level depression was not observed. Where users adequately engaged with the app, promising results were found highlighting the need for greater focus on engagement techniques in future research. CLINICALTRIAL Australian New Zealand Clinical Trials Registry ACTRN12620000178943; https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=378592