Unwanted outcomes in cognitive behavior therapy for pathological health anxiety: a systematic review and a secondary original study of two randomized controlled trials

IntroductionCognitive behavior therapy (CBT) is effective for pathological health anxiety, but little is known about unwanted outcomes.Areas coveredWe investigated unwanted outcomes in the form of adverse events, overall symptom deterioration, and dropouts in CBT for pathological health anxiety based on a systematic review of 19 randomized controlled trials (PubMed, PsycInfo, and OATD; last updated 2 June 2023; pooled N = 2188), and then a secondary original study of two randomized controlled trials (pooled N = 336). In the systematic review, 10% of participants in CBT reported at least one adverse event and 17% dropped out. Heterogeneity was substantial. In the original investigation, 17% reported at least one adverse event, 0-10% met criteria for overall symptom deterioration, and 10-19% dropped out. In guided Internet-delivered CBT, dropouts were more common with lower education and lower credibility/expectancy ratings. Higher adherence was associated with a larger reduction in health anxiety.Expert opinionUnwanted effects are routinely seen in CBT for pathological health anxiety, but, under typical circumstances, appear to be acceptable in light of the treatment's efficacy. There is a need for more consistent methods to improve our understanding adverse events, dropouts, and overall symptom deterioration, and how these outcomes can be prevented. People who worry excessively about having or developing a serious disease are commonly offered cognitive behavior therapy (CBT). Little is known about unwanted outcomes in CBT for this patient group. This study had two parts. First, we conducted a systematic search of the existing literature where we found that about 10% of patients in CBT experience an event that they perceive as unwanted or negative. About 17% of patients drop out of treatment prematurely. Results differed substantially between studies. Second, we analyzed the outcome of two original studies and found that about 17% of patients in CBT experience an event that they perceive as unwanted or negative. Patients who experienced such an event reported, on average, a smaller reduction in health anxiety if CBT was delivered face-to-face, but not if it was delivered via the Internet. About 0-10% rated their health anxiety as having become worse after CBT, and 10-19% dropped out prematurely. In CBT delivered via the Internet, patients were more likely to drop out if their level of education was lower, and if they rated the treatment as less credible and expectancy-evoking during week 2. We conclude that unwanted effects are relatively common but typically mild and acceptable.