Adverse event recording failed to reflect potential harms: a review of trial protocols of behavioral, lifestyle and psychological therapy interventions

•Harms or unintended consequences are known to be possible from trials of behavioral, lifestyle and psychological therapy interventions, yet are not always appropriately or consistently evaluated in trials.•Reliance on definitions for harms (typically termed adverse events) originally devised for pharmacological trials, may result in omission of important harms.•The level of risk or likelihood of harm from an intervention should always be assessed in trials of these interventions.•Better details on adverse event recording in protocols is needed to increase transparency and consistency and improve practice, but consensus is needed on the appropriate approach.•Examples of useful AE recording practices identified from trials included in this review are discussed, for example: alternative definitions of what constitutes a serious adverse event or methods of deriving lists of expected adverse events.