Effectiveness of Behaviour Change Techniques in Increasing Physical Activity and Improving Health‑Related Outcomes Among Patients with Severe Mental Illness in Secure Care Settings: A Systematic Review

Purpose This systematic review addresses a critical evidence gap in forensic mental health care. Adults with severe mental illness (SMI) - primarily schizophrenia-spectrum disorders and bipolar disorder - experience 15-20 year reduced life expectancy compared to the general population, largely due to preventable cardiometabolic diseases driven by sedentary lifestyles, obesogenic environments, and psychotropic medication side effects. Secure psychiatric settings (high-, medium-, and low-security forensic hospitals and locked wards) present unique challenges: restricted movement, high-calorie institutional diets, sedating medications, low motivation, and security constraints. Despite clear physical health benefits of exercise in community SMI populations, no comprehensive synthesis exists for structured physical activity interventions specifically within secure care. The review has three core aims: Identify all empirical studies evaluating structured physical activity interventions for SMI adults in secure settings Map intervention content to Michie's 93 Behaviour Change Techniques (BCT Taxonomy v1) to understand active ingredients Evaluate impact on physical health (weight, BMI, fitness), mental health (symptoms, mood), and behavioural outcomes (adherence, activity levels) Research Question Primary: How effective are behaviour change techniques embedded in physical activity interventions at improving health outcomes among adults with severe mental illness living in secure psychiatric settings? Secondary: Which BCTs are most commonly used in physical activity interventions at improving health outcomes among adults with severe mental illness living in secure psychiatric settings? How do these BCTs map to COM-B model components (capability, opportunity, motivation)? What is the methodological quality and risk of bias across studies? Methods Overview (PRISMA 2020) Eligibility (PICOST) Population: Adults (≥18) with diagnosed SMI in high-/medium-/low-security psychiatric/forensic settings Intervention: Structured physical activity/exercise programs (e.g. gym, walking, yoga, multi-component weight management) Comparator: Any/no comparator (including pre-post designs) Outcomes: Physical (weight/BMI/waist/fitness), mental (symptoms/mood), behavioural (steps/adherence) Study designs: Experimental, quasi-experimental, pre-post, cohort, feasibility, qualitative Timeframe: Inception to July 2026 Process Comprehensive search: 6 databases (PubMed, PsycINFO, CINAHL, EMBASE, Scopus, Cochrane) + grey literature Dual independent screening: Title/abstract - full-text (Cohen's κ reliability testing) Dual independent extraction: 550+ variables/study (study characteristics, outcomes, BCTs, ROBINS-I risk of bias) Synthesis: Narrative synthesis + BCT mapping to Behaviour Change Wheel/COM-B model Open science: Complete workflow (searches, screening decisions, raw extractions, reconciliation logs) shared FAIR-compliant on OSF Expected Outcomes Clinical findings (hypothesis) Based on preliminary evidence (e.g. Cormac 2008: -6.4kg weight loss), we anticipate: Modest short-term benefits for weight/BMI/waist circumference (most common outcomes) Mixed/uncertain mental health effects (few studies measure symptoms) Moderate feasibility (staff support overcomes security barriers) No harms reported across interventions Theoretical contribution Core BCT cluster: Goals & Planning (1.1) + Feedback & Monitoring (2.2, 2.3) + Social Support (3.1) + Environment Restructuring (12.1) COM-B emphasis: Motivation + Opportunity > Capability Mechanisms: Staff facilitation + environmental changes overcome security constraints Methodological findings High risk of bias: No RCTs; small samples (N=13-102); high attrition Evidence gaps: Long-term follow-up absent; objective PA measures rare; theory rarely explicit Deliverables PRISMA systematic review (narrative synthesis, BCT heatmaps, COM-B matrices) OSF repository (FAIR datasets: XLSX/CSV/JSON; screening logs; search strategies) Practice recommendations for secure care (staff training, minimal BCT package) Research agenda (RCTs with accelerometry, 12-month follow-up, theory-driven design) Significance This review will be the first comprehensive evidence synthesis for a high-risk, understudied population facing the largest physical health disparities in psychiatry. By linking intervention content (BCTs) to theoretical mechanisms (COM-B), it provides actionable guidance for practitioners while highlighting urgent trial needs. Timeline: Search complete July 2025; extraction February 2026; publication Q3 2026. OSF Registration DOI: [Auto-generated upon submission]