Purpose
Incidents of self-injury by forensic psychiatric patients often have a deleterious impact on all those involved. Moreover, self-injurious behaviour is an important predictor for violence towards others during treatment. The aim of this study is to analyse methods and severity of incidents of self-injury of patients admitted to forensic psychiatry, as well as the diagnoses of self-injuring patients.

Design/methodology/approach
All incidents of self-injury during treatment in a forensic psychiatric centre recorded between 2008 and 2019 were analysed and the severity was coded with the modified observed aggression scale+ (MOAS+).

Findings
In this period, 299 incidents of self-injury were recorded, displayed by 106 patients. Most of these incidents (87.6%) were classified as non-suicidal. Methods most often used were skin cutting with glass, broken plates, a razor or knife and swallowing dangerous objects or liquids. Ten patients died by suicide, almost all by suffocation with a rope or belt. The majority of the incidents was coded as severe or extreme with the MOAS+. Female patients were overrepresented and they caused on average three times more incidents than male patients.

Practical implications
More attention is warranted for self-injurious behaviour during forensic treatment considering the distressing consequences for both patients themselves, supervisors and witnesses. Adequate screening for risk of self-injurious behaviour could help to prevent this behaviour. Further research is needed in different forensic settings into predictors of self-injurious behaviour, more specifically, if there are distinct predictors for aggression to others versus to the self.

Originality/value
Incidents of self-injury occur with some regularity in forensic mental health care and are usually classified as severe. The impact of suicide (attempts) and incidents of self-injurious behaviour on all those involved can be enormous. More research is needed into the impact on all those involved, motivations, precipitants and functions of self-injurious behaviour and effective treatment of it.