Key recommendations:
➡️ Retrospective reporting can lead to inconsistent reporting on lifetime self-harm. Prospective designs will mitigate this.
➡️ Reporting the methods used to determine age of onset of self-harm will promote confidence in the findings

Main findings:
➡️ Age of onset often fell between 12-14 years
➡️ Cross-sectional methods (81%) and use of retrospective report (71%) was common
➡️ Self-harm was commonly described as either suicidal or non-suicidal
➡️ 38% of studies did not report the methods used to capture age of onset