Substance use does not predict schizophrenia self-harm, violence

By Lucy Piper, Senior medwireNews Reporter

Substance misuse, although common among people with schizophrenia, does not heighten their risk for self-harm or violence, study findings show.

Rather, it is the type of psychotic symptoms experienced by patients with schizophrenia and comorbid substance use that largely determines the occurrence of such behaviors.

Researchers, led by Gillian Haddock (University of Manchester, UK), recruited 327 patients with schizophrenia and comorbid substance use, 93 of whom had self-harmed over a 2-year period.

After adjusting for substance use (percentage of days abstinent from all substances), patients with delusions were 1.4-fold more likely to self-harm than others, and the risk increased 1.1-fold among those distressed by their delusions.

Of the 327 patients studied, 157 (48%) had threat control override symptoms and their risk for self-harm was twice that of those without such symptoms. Similarly, the 39 (11.9%) participants with command hallucinations had a 2.7-fold increased risk for self-harm.

By contrast, the presence of delusions, threat control override symptoms, or command hallucinations were not associated with violence to others, reported by 32.3% of patients; although delusions, surprisingly, were negatively associated with the number of physically violent incidents.

There was exploratory evidence suggesting that specific types of command hallucinations may play different roles in violent behavior, in that benign command hallucinations were associated with more incidents of physical violence, whereas commands to self-harm were associated with more incidents of self-harm. However, the number of patients experiencing each command subtype was small.

“The findings highlight that a careful understanding of the nature of the content of individual’s symptoms, as well as their severity and the level of distress related to them, appears important to understand [the] complex relationships between psychotic experiences, harm to others, and self-harm,” the researchers write in Schizophrenia Research.

“This relationship is largely unaffected by the severity of substance use within this population.”

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