Patterns of substance abuse in offenders court-referred for pre-sentence evaluation: associations with mental disorder and offending behaviour

The research literature reflects growing concern about the impact of substance use disorder (SUD) and the extent to which it may contribute to offending behaviour. The broad aims of this thesis were to 1) explore patterns and associations between SUD and substance use variables in a sample of offenders; 2) examine the relationship between SUD and mental disorder; 3) explore associations between substance use and offending behaviour; and 4) examine the combined effect of SUD with mental disorder and antisocial personality disorder on offending behaviour. Participants comprised 87 offenders who attended the Community Forensic Mental Health Service in Victoria, Australia for court-referred pre-sentence psychological or psychiatric evaluation. Results revealed a high prevalence of mental disorder, with 87% of participants meeting diagnostic criteria for at least one DSM-IV Axis I or Axis II mental disorder. These disorders rarely occurred in isolation, with results indicating a high level of psychiatric comorbidity. Participants with SUD suffered significantly higher rates of psychiatric morbidity when compared to their non-disordered counterparts; 93.2% of the participants with lifetime SUD met criteria for an additional mental disorder. Significant associations between lifetime SUD and offending behaviour were revealed, including a higher likelihood of violent offending, higher severity and versatility in offending, and a higher rate of imprisonment. Severity of substance use was also significantly associated with offending variables, and there was evidence that the relationship between substance use and offending varied according to substance and offence type. By distinguishing between substance using offenders by age at onset of SUD, this study revealed significant associations between early-onset SUD and a higher rate of current and lifetime substance dependence, a higher prevalence of polysubstance dependence and multiple SUD diagnoses, and higher severity of substance use. Early-onset SUD was also associated with offending behaviour, including a higher likelihood of juvenile offending, a higher likelihood of violent offending, greater criminal versatility, higher frequency and severity in offending, and a higher likelihood of imprisonment. This study also considered acquisitive, psychopharmacological and antisocial lifestyle explanations for the association between substance use and offending behaviour. Results showed that offenders with SUD were disproportionately represented within offence categories of acquisitive crime. Participants with a history of acquisitive offending met criteria for multiple SUD diagnoses significantly more frequently, and had significantly higher levels of substance use severity. In support of the psychopharmacological explanation for the association between acute substance use and offending, a very high proportion of participants with lifetime SUD had a history of offending whilst under the influence of alcohol or illicit substances. Results also supported the hypothesis that violent offending would be more strongly related to acute alcohol use than acute illicit substance use. Finally, the substance using offenders presented with a range of antisocial lifestyle factors, including higher levels of antisocial attitudes and association with antisocial peers, higher levels of antisocial personality pathology, and higher levels of criminal behaviour. These latter findings are consistent with the antisocial lifestyle thesis. In summary, the study findings suggest that it is unlikely that a single explanation can adequately account for the relationship between substance use and offending. Rather, it appears that each of the explanations explored assist understanding of the substance use-offending relationship. A primary aim of this research was that it would assist in the development of improved methods for assessing and treating substance-using offenders. The results show that substance-using offenders represent a heterogeneous population with respect to their history of substance use, psychopathology, and offending behaviours; thereby encouraging interventions that are comprehensively tailored to individual needs