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OBJECTIVE: If a psychotherapeutic intervention has the capacity to produce positive change, the "deterioration effect" theory holds that it must also have the potential for negative effects. However, the definition, measurement, and reporting of unwanted events in psychotherapy is a topic of ongoing discussion. At present this area is under-explored in interventions for anorexia nervosa (AN), a severe mental illness associated with high medical and psychiatric risks. The aim of this article was to undertake a systematic review of published randomized controlled trials (RCTs) evaluating psychotherapeutic interventions for AN, and to assess how unwanted events were defined, monitored, and reported alongside the trial's key findings. METHOD: Using a systematic review methodology, this article identified 23 RCTs through database searches meeting eligibility criteria. Results are presented using a narrative summary approach. RESULTS: Unwanted event reporting varied widely, both regarding definitions of key unwanted events (such as non-compliance or symptom deterioration) and in the amount of detail captured in each paper. DISCUSSION: The review identified two key issues: firstly, a lack of consistent definitions and unclear causality made it difficult to distinguish between unwanted events, and adverse events caused by the interventions. Secondly, it highlighted the difficulty of defining unwanted events where different studies have different populations and goals. Recommendations are made around how the area of defining, monitoring, and reporting unwanted events in RCTs for AN can be taken forward. PUBLIC SIGNIFICANCE: Whilst psychotherapies can be effective in treating mental health conditions, negative or unwanted events can sometimes occur. This review explored how RCTs examining psychotherapy for AN report how they monitor the safety of participants, and how they report unwanted events. We found that the reporting was often inconsistent or hard to interpret, and we have made recommendations for how this can be improved in the future.

Original publication




Journal article


Int J Eat Disord

Publication Date



adverse events, anorexia nervosa, eating disorders, psychotherapy, randomized controlled trials, systematic review, unwanted events