Investigating the Efficacy of the Web-Based Common Elements Toolbox (COMET) Single-Session Interventions in Improving UK University Student Well-Being: Randomized Controlled Trial
Authors: Lambert Jeffrey , Loades Maria , Marshall Noah , Higson-Sweeney Nina , Chan Stella , Mahmud Arif , Pile Victoria , Maity Ananya , Adam Helena , Sung Beatrice , Luximon Melanie , MacLennan Keren , Berry Clio , Chadwick Paul 
Published: January 2025

Background
Mental health problems in university students are associated with many negative outcomes, yet there is a gap between need and timely access to help. Single-session interventions (SSIs) are designed to be scalable and accessible, delivering core evidence-based intervention components within a one-off encounter.

Objective
COMET (Common Elements Toolbox) is an online self-help SSI that includes behavioral activation, cognitive restructuring, gratitude, and self-compassion. COMET has previously been evaluated in India, Kenya, and the United States with promising results. This study tests the acceptability, appropriateness, perceived utility, and efficacy of COMET among UK university students during the peripandemic period.

Methods
We conducted a randomized controlled trial evaluating the efficacy of COMET compared with a control group, with 2- and 4-week follow-ups. Outcome variables were subjective well-being, depression severity, anxiety severity, positive affect, negative affect, and perceived stress. We also measured intervention satisfaction immediately after completion of COMET. All UK university students with access to the internet were eligible to participate and were informed of the study online. The data were analyzed using linear mixed models and reported in accordance with the CONSORT-EHEALTH (Consolidated Standards of Reporting Trials of Electronic and Mobile Health Applications and Online Telehealth) checklist.

Results
Of the 831 people screened, 468 participants were randomized to a condition, 407 completed the postintervention survey, 147 returned the 2-week follow-up survey, 118 returned the 4-week follow-up survey, and 89 returned both. Of the 239 randomized, 212 completed COMET. Significant between-group differences in favor of the COMET intervention were observed at 2-week follow-ups for subjective well-being (Warwick-Edinburgh Mental Well-Being Scale; mean difference [MD] 1.39, 95% CI 0.19-2.61; P=.03), depression severity (9-item Patient Health Questionnaire; MD –1.31, 95% CI –2.51 to –0.12; P=.03), and perceived stress (4-item Perceived Stress Scale; MD –1.33, 95% CI –2.10 to –0.57; P<.001). Overall, participants were satisfied with COMET, with the majority endorsing the intervention and its modules as acceptable, appropriate, and exhibiting high utility. The self-compassion module was most often reported as the participants’ favorite module and the behavioral activation module was their least favorite. Qualitative analysis revealed that participants found COMET generally accessible, but too long, and experienced immediate and long-term beneficial effects.

Conclusions
This study demonstrated high engagement with the COMET intervention, along with preliminary short-term efficacy. Almost all participants completed the intervention, but study attrition was high. Participant feedback indicated a high level of overall satisfaction with the intervention, with perceived accessibility, immediate benefits, and potential long-term impact being notable findings. These findings support the potential value of COMET as a mental health intervention and highlight important areas for further improvement.

Trial Registration
ClinicalTrials.gov NCT05718141; https://clinicaltrials.gov/ct2/show/NCT05718141