Abstract
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.
. Introduction
Research suggests that rates of violence and self-harm are higher in people with schizophrenia than in other diagnostic groups (Arsenault et al., 2000, Schanda et al., 2004 and Walsh et al., 2004). Self-harm is common (Haw et al., 2005), although the prevalence of violence to others remains unclear (Walsh et al., 2004). The relationship between violence and schizophrenia is complex and a number of factors have been shown to increase the risk of violence, including specific positive symptoms and substance use, as well as social deprivation, male gender, and younger age (Bo et al., 2011 and Witt et al., 2013).
In terms of specific positive symptoms, threat control override symptoms, command hallucinations and persecutory delusions/hallucinations (Bjorkly, 2002, Frasán et al., 2005, Erkiran et al., 2006 and Swanson et al., 2006), have all been shown to increase the risk of violent behaviour towards others in individuals with schizophrenia. Research also suggests that feelings of distress in relation to positive symptoms may also predict violence (Bjorkly, 2002 and Van Dongen et al., 2012). Although self-harm has been more strongly associated with depression than positive psychotic symptoms (Harvey et al., 2008 and Pluck et al., 2012), there is some evidence to suggest that positive symptoms may also influence self-harm and suicidal behaviour (Hodgins et al., 2003).
Substance misuse is common in schizophrenia, with prevalence estimates of 40–50%, compared to 16% in the general population (NICE, 2009). When substance use is linked with schizophrenia, rates of violence have been shown to be consistently higher (Wallace et al., 2004, Foley et al., 2005, Erkiran et al., 2006 and Fazel et al., 2009), although not exclusively so (Modestin and Wuermle, 2005). Research suggests that substance use can exacerbate positive symptoms in individuals with schizophrenia (Margolese et al., 2004 and Kerfoot et al., 2011), and both appear to predict violence, yet the interaction between these two variables and their effect on violent behaviour and self-harm remains unclear.
We therefore aimed to explore rates of violence and self-harm in a sample of people with schizophrenia dually diagnosed with substance misuse and to test the hypotheses that severity of specific psychotic symptoms (delusions and hallucinations) would not be associated with violence (to others or to self) once substance use was controlled for. In addition, we explored how psychotic symptom distress was related to violence and self-harm.
