Psychotic symptoms, self-harm and violence in individuals with schizophrenia and substance misuse problems

When schizophrenia is combined with substance misuse, rates are consistently higher. However research findings on the relationship between violence, self-harm and schizophrenia are inconclusive. This study aimed to examine links between specific psychotic symptoms, substance misuse and violence in people dually diagnosed with schizophrenia and substance misuse. Presence and frequency of violence to self and others were examined in relation to the type and severity of psychotic symptoms and level of substance use over a 24 month period in 327 people with schizophrenia and substance misuse problems. 32.3% had an incident of violence to others during the study period and 28.6% had a self-harm/suicide incident. 39 (11.9%) participants reported command hallucinations (CH) and 157 (48.0%) had threat control override symptoms (TCOS). Presence of TCOS and presence of CH were not associated with violence to others but were both associated with self-harm. Different command hallucination sub-types were associated with different types of violence. Delusional and hallucination severity and distress were mainly associated with self-harm. These findings suggest that specific symptoms are related to different outcomes, particularly in relation to self-harm, and these effects remain even after substance use is controlled for. This has important implications for assessment and treatment of this group.