There is a link between self–harm and the risk of violent criminality, according to a Swedish registry study carried out by researchers at Karolinska Institutet and published in the journal JAMA Psychiatry.

Deliberate self–harm, such as cutting, burning or overdosing on drugs to escape distressing emotions or attempt suicide is a serious and common behaviour.

It has long been suspected that individuals who self–harm may also be prone to aggressive behaviours towards others, but the studies that have been conducted thus far have not been able to give conclusive answers. Researchers at Karolinska Institutet have therefore used Swedish registries to investigate the link between deliberate self–harm and violent crime convictions. The registries give unique opportunities to study this correlation since they cover the entire population.

The study included all Swedish citizens born between 1982 and 1998 and followed them from age 15 (1,850,525 individuals in total). During the study period 55,185 received self–harm associated clinical care, 66,561 were convicted of a violent crime, and 8,155 were both exposed to self–harm and convicted of a violent crime. Individuals who had at some time received clinical care for self–harm ran a five–fold risk of being convicted for a violent crime compared with those who had never received care for self–harm.

“A susceptibility to self–harm seems to increase the risk of violent expression, but we found no support for the hypothesis that self–harm causes violence crime,” says Hanna Sahlin, doctoral student at the Department of Clinical Neuroscience at Karolinska Institutet. “When we reversed the analysis and examined the risk of self–harm in individuals convicted of a violent crime, we found a similar association. Taken together, this suggests that self–harm behaviour and violent criminality is a manifestation of a common underlying vulnerability.”

Almost as many men as women received clinical care for self–harm during the study period. The risk of violent crime conviction was particularly high for self–harming women with comorbid substance abuse, with a seven times increased risk for violent crime conviction, compared to women who had never received clinical care for self–harm.

Even after controlling for relevant confounders, such as psychiatric co–morbidity and socioeconomic factors, self–harm was still associated with a doubled risk of violent crime conviction, a finding that remained when men and women were analysed separately.

“We need to ask about aggressive behaviour towards others when we assess and treat self–harming individuals, but we also need to ask about self–harm when we assess and treat aggressive individuals,” says Ms Sahlin.