Studying adverse events in psychotherapy is challenging because these events are sparsely reported by research, and reporting tends to be unsystematic with varying definitions. This contrasts with medical intervention studies, in which reporting adverse events is very common and is based on well-accepted definitions. An adverse event in psychotherapy studies might include any negative change in patients' physical or mental health. A serious adverse event could consist of enduring severe impairment, deterioration of symptoms for more than two weeks, suicidality, or death. There are other complications to studying adverse events in psychotherapy. First, a patient who experienced an adverse event might have had one anyway even without psychotherapy. Second, psychotherapy may have prevented an adverse event for some patients, but this is impossible to document . And third, some patients may deteriorate as a result of psychotherapy, and deterioration might not have occurred without treatment. Population-based surveys suggest that 57.8% of patients experienced unpleasant memories while in psychotherapy, and 15% in another survey reported lasting negative effects of psychotherapy. In this systematic review, Klatte and colleagues were interested in characterizing the reporting of adverse events in randomized controlled psychotherapy trials. Eighty-five studies were included in their review, consisting of 14,420 patients with common mental disorders (depression, anxiety, personality disorders). Only 60% of studies reported adverse events (individuals with symptom deterioration), and defining adverse events was highly variable across studies. As a result, it remained unclear what percentage of the adverse events were caused specifically by the psychotherapies. On average, in those studies reporting adverse events, one in 10 (10%) patients experienced one or more adverse events, while one in 20 (5%) reported a severe adverse event.
Practice Implications
Population surveys indicate that severe adverse events are common. However, it is unclear whether these patients deteriorated due to treatment. Regardless, some patients’ functioning may worsen. We know that psychotherapy providers are not accurate in detecting patients who get worse – that is, therapists often underestimate the number of their patients who deteriorate. Therefore, therapists need help with procedures like routine outcome monitoring to assess their patients’ progress. With such information, therapists can make appropriate adjustments to help their patients who experience an adverse event.
Klatte, R., Strauss, B., Flückiger, C., & Rosendahl, J. (2025) Adverse events in psychotherapy randomized controlled trials: A systematic review. Psychotherapy Research, 35, 84-99. https://doi.org/10.1080/10503307.2023.2286992
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