Abstract
OBJECTIVE: A sudden gain is defined as a large and stable individual improvement occurring between two consecutive treatment sessions. Sudden gains have been shown to predict better long-term improvement in several treatment studies, including cognitive behavioural therapy for depression and anxiety disorders, but have not been studied in the treatment of health anxiety or any form of internet-based cognitive behavioural therapy. The aim of this study was to investigate the role of sudden gains in internet-based cognitive behavioural therapy for severe health anxiety. METHOD: We examined the occurrence and significance of sudden gains in measures of health anxiety in 81 participants receiving internet-based cognitive behavioural therapy. We compared patients with sudden gains, patients without sudden gains, and patients with gradual gains. RESULTS: Thirteen participants (16%) experienced one sudden gain in health anxiety with individual sudden gains distributed across the treatment. As expected, patients with a sudden gain showed larger improvements than patients without a sudden gain at post-treatment (d = 1.04) and at one-year follow-up (d = 0.91) on measures of health anxiety. CONCLUSIONS: Consistent with previous studies, sudden gains in internet-based cognitive behavioural therapy are associated with significantly larger and stable treatment effects up to one-year follow-up.