Background: Delivery of preventative interventions via mobile phone applications offers an effective and accessible way to address the global priority of improving the mental health of adolescents and young adults. A proven risk factor for anxiety and depression is elevated worry and rumination, also known as repetitive negative thinking (RNT).Objective: This was a prevention mechanism trial testing whether an RNT-targeting self-help mobile phone application (MyMoodCoach) reduces worry and rumination in young adults residing in the United Kingdom. A secondary objective was to test whether the app reduces symptoms of anxiety and depression and improves well-being.Methods: A web-based, single-blind, two-arm parallel-group Randomised Controlled Trial (RCT) was conducted with N=236 people aged between 16 and 24 who self-reported high levels of worry or rumination. Eligible participants were randomised to an active intervention group (usual practice, plus up to 6 weeks of using the RNT-targeting mobile app, n=119) or a waitlist control group (usual practice with no access to the app until after six weeks, n =117). The primary outcome was changes in worry and rumination six weeks after randomisation. Secondary outcomes included changes in well-being and symptoms of anxiety and depression after six weeks and changes on all measures after 12 weeks.Results: Participants randomly allocated to use the RNT-targeting self-help app showed significantly lower levels of rumination (mean difference -2.92, 95% CI [-5.57, -.28], P =.031, ?p2 = .02) and worry (mean difference -3.97; 95% CI [-6.21, -1.73], P <.001, ?p2 = .06) at six-week follow-up, relative to the waitlist control. Similar differences were observed for wellbeing (P <.001), anxiety (P = .03) and depression (P = .04). The waitlist control group also showed improvement when given access to the app after six weeks. Improvements observed in the intervention group after 6 weeks of using the app were maintained at the 12-week follow-up point.
Conclusions:The MyMoodCoach app had a significant positive effect on worry and rumination, well-being, anxiety, and depression in young adults, relative to waitlist controls, providing proof-of-principle that an unguided self-help app can effectively reduce repetitive negative thinking. This app therefore has potential for prevention of anxiety and depression although longer-term effects on incidence need to be directly evaluated. Clinical Trial: ClinicalTrials.gov, NCT04950257. Registered 6 July 2021 -Retrospectively registered (shortly after start of recruitment), https://www.clinicaltrials.gov/ct2/show/NCT04950257