A pilot randomized controlled trial of a transdiagnostic multidomain lifestyle intervention for psychiatric outpatients: feasibility, acceptability and preliminary effectiveness for improving recovery

People with mental illness often face psychosocial challenges, somatic comorbidities, and limited response to symptom-focused treatment, highlighting the need for effective recovery-oriented strategies. Lifestyle interventions are promising for improving recovery, but evidence on multidomain interventions in transdiagnostic samples is limited. This pilot randomized controlled trial aimed to evaluate the feasibility, acceptability and preliminary effectiveness of a transdiagnostic multidomain lifestyle intervention adapted for psychiatric outpatients. Forty-six outpatients were randomized (1:1) to receive the intervention (12 weekly group sessions + 3 follow-up sessions) or treatment-as-usual. The intervention targeted multiple lifestyle domains: physical activity, nutrition, relaxation, sleep, substance use, spirituality, social participation, and nature. Outcomes included feasibility (recruitment, retention, adherence), acceptability (participant evaluations, trainer feedback) and preliminary exploratory effectiveness (self-report questionnaires and physical measurements on several recovery outcomes, including the Recovery Assessment Scale as primary effect measure). Outcomes were administered at baseline, post-intervention and follow-up. The intervention and research protocol appeared feasible and acceptable. This is reflected by relatively high intervention attendance (71%) and a low dropout rate (13%). Overall study retention was 83%. Participants rated the intervention 7.4/10 and particularly valued the topic relaxation and spirituality . The intervention content and its difficulty were reported as appropriate. The intervention appears suitable for real-world implementation in clinical practice, with minimal risks reported by trainers and participants. However, organizational factors such as staff capacity, high workload and organizational instability require attention. Exploratory analyses suggested positive trends across various recovery domains; notably on long-term for societal and personal recovery. However, effect estimates were imprecise (95% CI including zeros) and these exploratory findings should be interpreted with caution. Based on this pilot, inclusive multidomain lifestyle interventions in specialist mental healthcare appear feasible and well-received by a heterogeneous sample of mental illness. Results encourage further testing in a fully powered trial. This trial preregistered at 30-05-2023 at Overview of Medical Research in the Netherlands with trial registration number: NL-OMON53239, CCMO register number: NL83935.042.23.