Co-designing and piloting adolescent-adapted social rhythm therapy for young people with unipolar and bipolar depression: a mixed-methods feasibility case series.

Objective: Depressive and bipolar disorders commonly emerge during adolescence and are associated with disturbances in sleep, daily routines and social rhythms, as well as functional impairment. Social Rhythm Therapy (SRT) targets these processes. However, adult-derived rhythm protocols do not adequately reflect adolescents' school and family schedules, developmental autonomy, social and digital routines, or preferences regarding monitoring. Direct youth co-design is therefore needed to improve developmental fit, engagement and feasibility. We addressed this gap by co-designing the Social Therapy for Adolescent Rhythms in Depression (STAR-D), an adolescent-adapted SRT intervention, and evaluating its feasibility and acceptability within routine Child and Adolescent Mental Health Services (CAMHS). Methods: A two-phase mixed-methods feasibility design was used. Phase 1 involved co-production and intervention adaptation using questionnaire feedback from 10 adolescents, an in-depth interview with one Young People's Advisory Group representative, and feedback from six clinicians. TIDieR principles guided intervention description and adaptation. Phase 2 piloted STAR-D in adolescents receiving care in Lambeth CAMHS, London, UK. Feasibility was assessed through referral, uptake, retention and completion. Acceptability was assessed through qualitative feedback. Exploratory clinical outcomes were described using measures of functioning, depressive symptoms and manic symptoms. Results: Phase 1 feedback identified priorities for intervention adaptation, including accessible language, explicit links between routines and mood, personalised goals and flexible delivery. These findings informed an eight-session STAR-D protocol. In Phase 2, seven young people were referred, six accepted and started STAR-D, and five completed all eight sessions. Participants described the intervention as supportive, collaborative and accessible. However, they suggested simplifying daily monitoring to reduce burden. Quantitative completion and missingness data for monitoring forms were not prospectively collected. Exploratory clinical trajectories were variable. Conclusion: STAR-D was feasible to deliver and acceptable to most participants in this small, uncontrolled, single-service pilot. The findings support further optimisation, particularly of routine monitoring, followed by a larger multicentre controlled mechanistic trial. Future work should test whether changes in sleep-wake regularity, daily routines and social rhythm stability mediate changes in mood and functioning, and should evaluate unipolar and bipolar presentations with sufficient diagnostic stratification.