Psychotic symptoms, self-harm and violence in individuals with schizophrenia and substance misuse problems Gillian Haddock ⁎, Emily Eisner, Gabriel Davies, Nia Coupe, Christine Barrowclough abstract article info Article history: Received 27 June 2013 Received in revised form 16 October 2013 Accepted 25 October 2013 Available online 20 November 2013 Keywords: Schizophrenia Substance misuse Psychosis Dual diagnosis Violence Self harm Positive symptoms Hallucinations Delusions When schizophrenia is combined with substance misuse, rates are consistently higher. However research find- ings 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 symp- toms (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. © 2013 Elsevier B.V. All rights reserved. 1. 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; Walsh et al., 2004). Self-harm is com- mon (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 youn- ger age (Bo et al., 2011; 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; Swanson et al., 2006), have all been shown to increase the risk of violent behaviour towards others in individuals with schizo- phrenia. Research also suggests that feelings of distress in relation to positive symptoms may also predict violence (Bjorkly, 2002; Van Dongen et al., 2012). Although self-harm has been more strongly as- sociated with depression than positive psychotic symptoms (Harvey et al., 2008; Pluck et al., 2012), there is some evidence to suggest that positive symptoms may also influence self-harm and suicidal behav- iour (Hodgins et al., 2003). Substance misuse is common in schizophrenia, with prevalence esti- mates of 40–50%, compared to 16% in the general population (NICE, 2009). When substance use is linked with schizophrenia, rates of vio- lence have been shown to be consistently higher (Wallace et al., 2004; Foley et al., 2005; Erkiran et al., 2006; 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; Kerfoot et al., 2011), and both ap- pear 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 relat- ed to violence and self-harm. 2. Methods 2.1. Subjects The 327 study participants were recruited from 6 large Community Mental Health Teams in North West England and London regions, UK, Schizophrenia Research 151 (2013) 215–220 ⁎ Corresponding author at: School of Psychological Sciences, Zochonis Building, The University of Manchester, Brunswick Street, Manchester M13 9PL, UK. Tel.: +44 161 275 8485; fax: +44 161 275 8487. E-mail address: Gillian.Haddock@Manchester.ac.uk (G. Haddock). 0920-9964/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.schres.2013.10.031 Contents lists available at ScienceDirect Schizophrenia Research journal homepage: www.elsevier.com/locate/schres