Substance dependence and schizophrenia in patients with dangerous, violent and criminal propensities: a comparison of co-morbid and non-co-morbid patients in a high-security setting

Abstract

Studies show that schizophrenia is associated with increased substance misuse/dependence. An association exists between co-morbidity and violence/offending. Our aim was to compare substance-dependent and non-substance-dependent patients with schizophrenia, by using patient interviews and retrospective case-note data. A sample of 169 patients with schizophrenia in high-security psychiatric care was divided into two groups by using the absence/presence of substance dependence. Diagnoses were made using St Louis criteria. Of the patients, 88.8% were male. Lifetime rates of substance misuse showed that 53.8% had a history of alcohol misuse and that 53.3% had a history of drug misuse. Co-morbid substance dependence was present in 41.4% and schizophrenia alone in 58.6%. Co-morbid patients were more likely to be from the west of Scotland, to have a history of convictions and to be intoxicated prior to admission. They were more likely to be treated with anti-cholinergics or anti-depressants, to suffer affective symptoms or to have anti-social personality disorder. They were less likely to have negative symptoms, thought disorder, or learning disability and less likely to be civilly detained. This study finds high rates of substance misuse/dependence occurring co-morbidly with schizophrenia in Scottish high-security settings. Co-morbidity is associated with increased offending. Differences in symptom profiles and demographics may have potential implications for recognition and risk management.