Patterns of co-morbidity between Axis II personality disorders and Axis I clinical syndromes may indicate unmet needs, suggest future treatment interventions and determine admission to secure hospital facilities. Inter- and intra-axis co-morbidity was examined in 260 male and female offenders in high-security hospitals and special units for high-risk prisoners, using research diagnostic interviews. Logistic regression was used to control for confounding between diagnostic categories. Although previously observed patterns of co-morbidity were confirmed, the overall level of Axis II-Axis II co-morbidity was considerably lower than in previous studies, especially for borderline personality disorder. Borderline personality disorder was highly co-morbid with lifetime Axis I affective and neurotic disorders, psychotic episodes and transsexualism. Anti-social personality disorder was co-morbid with Axis II narcissistic, paranoid, borderline and passive-aggressive personality disorders, reflecting serious offending behaviour and high levels of psychopathy in the sample. Certain Axis II disorders may convey increased risk for lifetime Axis I disorder. But some patterns of co-morbidity may be artefacts of the DSM diagnostic system. Future studies of Axis II co-morbidity should apply appropriate statistical methods and include Axis I disorders.
