Abstract
BACKGROUND: Clients independently applying Cognitive Behavior Therapy (CBT) skills is an important outcome of CBT-based treatments. The relationship between posttherapeutic CBT skills usage and clinical outcomes remains under-researched-especially after internet-delivered CBT (iCBT). OBJECTIVE: Explore contemporaneous and lagged effects of posttherapeutic CBT skills usage frequency on iCBT follow-up outcomes. METHOD: Nested within a randomized controlled trial, 241 participants received 8-week supported iCBT for anxiety and/or depression, completing measures of anxiety, depression, functional impairment, and CBT skills usage frequency at 3-, 6-, 9-, and 12-month follow-up. Cross-lagged panel models evaluated primary aims. RESULTS: While analyses support a contemporaneous relationship between anxiety, depression, functional impairment, and CBT skills usage frequency, no consistent lagged effects were observed. CONCLUSION: Findings align with qualitative research but the role of CBT skills usage in the maintenance of iCBT effects remains unclear. Innovative research modeling temporal and possibly circular relationships between CBT skill usage and clinical outcomes is needed to inform iCBT optimization.