Effectiveness of cognitive behavioural therapy on anxiety and depression symptoms in naturalistic settings for patients with and without personality disorders

OBJECTIVES: Personality disorders (PD) are often considered a negative prognostic factor for cognitive behavioural therapy (CBT) in anxiety and depression, yet evidence from real-world settings with rigorous diagnostic assessment remains limited. This study examined whether PD diagnosis influences CBT outcomes using data from inTHERAPY, an Italian CBT service integrating systematic outcome monitoring with structured diagnostic assessment (SCID-5). METHODS: Patients receiving CBT for anxiety and/or depression were classified according to the presence or absence of a PD and assessed on anxiety, depression, and psychosocial functioning. Treatment effectiveness was evaluated through symptom change, reliable and clinically significant improvement (RCSI), and recovery rates. Mixed-effects growth curve models examined outcome trajectories, and regression analyses tested the role of PD diagnosis, treatment exposure, and dropout status. RESULTS: CBT was associated with a RCSI rate of 50%, with moderate-to-large pre-post effect sizes for anxiety (d = .77), depression (d = .76), and functioning (d = .63). Although patients with PD presented with higher baseline severity and lower recovery rates, PD diagnosis did not independently predict outcomes when baseline severity, dropout status, and number of sessions were controlled for. Symptom trajectories were nonlinear and largely comparable across groups. Notably, patients with PD who dropped out late showed greater functional impairment at discharge than late dropouts without PD. CONCLUSIONS: These findings suggest that standard disorder-specific CBT is effective for patients with comorbid PD in real-world practice. Apparent poorer outcomes primarily reflect greater initial severity, underscoring the importance of adequate treatment duration and strategies to prevent late dropout.