NDARC Monograph No. 32 (1997)
Antisocial personality disorder (ASPD) is one of the most frequent diagnoses given to injecting drug users (IDUs) and is often regarded as co-extensive with the older concept of "psychopathy". It has been argued, however, that the illegal nature of injecting drug use inflates the proportion of this group who are considered psychopaths and that the prevalence will be much lower when the core psychological characteristics of psychopathy are considered.
A sample of 200 community methadone (CM) patients, 200 prison methadone (PM) patients, and 150 prison inmates with no history of heroin dependence (PNH) were interviewed using the DIS for a DSM-III-R diagnosis of ASPD and for a diagnosis of psychopathy, using the Psychopathy Checklist-Revised (PCL-R).
The proportions receiving diagnoses of ASPD and psychopathy, respectively, were CM (44% v 4%), PM (65% v 9%), and PNH (31% v 4%). In all cases, the proportions receiving ASPD diagnoses were significantly greater than concurrent diagnoses of psychopathy using the PCL. PM patients had significantly higher proportions of ASPD diagnoses than either of the other two groups. The prevalence of psychopathy did not differ between groups. Of those subjects who received a diagnosis of ASPD, only 11% also qualified for a diagnosis of psychopathy. Conversely, 94% of those who received a diagnosis of psychopathy also received a diagnosis of ASPD. Lack of remorse, the sole psychological symptom of ASPD, was present in 33% (CM), 36% (PM), and 61% (PNH) of those who received an ASPD diagnosis.
Those subjects whose criminal careers had preceded their drug-using careers were similar to those whose drug use preceded their criminal activity in terms of their drug use and treatment histories, but were more likely to have committed violent crimes to qualify for a diagnosis of ASPD (63% v 30%). There was no significant difference found between these two groups with respect to the prevalence of psychopathy (8% v 4%), but it is noted that the associated confidence interval was wide and should thus be interpreted with caution.
A diagnosis of ASPD was not related to performance in methadone maintenance treatment for either the CM or PM groups. In both groups there were no significant differences in methadone dose, time retained in treatment, proportions who had used heroin or other opioids recently, and proportions who had recently borrowed or lent needles.
The two-factor structure (behavioural and psychological) of psychopathy hypothesised by Hare was not replicated by confirmatory factor analyses. A more complex five-factor solution was generated which comprised three psychological factors, and two behavioural factors.
In summary, the present study demonstrated a marked discrepancy between the prevalence of ASPD and psychopathy among both injectors and non-injectors. When DSM-III-R criteria were applied, "psychopathy" was diagnosed in over half of IDUs and almost a third of non-IDUs. However, when the PCL-R was used, the prevalence of psychopathy fell to 7% among IDUs and 4% among non-IDUs. The likelihood of diagnosing "psychopathy" among both these populations, therefore, varies enormously, depending upon the diagnostic system that is used. ASPD appears to be a behavioural, rather than a personality, disorder and should not be equated with psychopathy.