Exposure-based cognitive behavioral therapy delivered by assertive community treatment teams for severe mental illness with symptoms of anxiety: a cluster randomized controlled trial

Background Individuals with severe mental illnesses (SMIs) experience anxiety that impairs functioning and quality of life. This cluster randomized trial evaluated exposure-based cognitive behavioral therapy (ebCBT) integrated into assertive community treatment (ACT) teams to reduce anxiety. Methods Fifteen ACT teams were allocated to ebCBT + ACT (k = 8, n = 50) or ACT-only (k = 7, n = 43). The intervention followed four steps: situation identification, four-component analysis (behavior, cognition, emotion, physical symptoms), psychoeducation, and graded exposure. Staff received 50 h training and bimonthly supervision over 12 months. Co-primary outcomes were trait and social anxiety; secondary outcomes were psychiatric symptoms, functioning, quality of life, and recovery. Results The ebCBT + ACT group showed significant improvements in State–Trait Anxiety Inventory–Trait scores at 12 months (AMD = −5.30, 95% CI = −8.71 to −1.90, p = 0.002, d = −0.64) and 18 months (AMD = −7.22, 95% CI = −12.1 to −2.34, p = 0.004, d = −0.60). Brief Fear of Negative Evaluation scores showed near-significant improvement at 18 months (AMD = −3.70, 95% CI = −7.44 to 0.04, p = 0.052, d = −0.40). Secondary outcomes, including global functioning, recovery, and quality of life, also improved. Cost-effectiveness analyses indicated favorable cost-effectiveness for anxiety outcomes. Conclusions Embedding ebCBT within ACT services may reduce anxiety-related fear and avoidance and enhance recovery-related outcomes in individuals with SMI. These findings support the feasibility and clinical value of integrating structured psychological interventions into intensive community-based outreach services.