The review found that adverse events in psychotherapy trials are inconsistently defined, measured, and reported, making it difficult to accurately estimate the risks associated with treatment. Across the included studies, harmful events were reported in a substantial proportion of participants, with serious adverse events occurring in more than one in twenty individuals. However, the relationship between reported events and the psychotherapy itself was often unclear due to inconsistent monitoring procedures. Overall, the findings highlight the need for routine, standardised harm assessment and reporting to enable balanced evaluations of the benefits and risks of psychotherapy.