The concept of personality disorder (PD) is more relevant in the clini
cal management of drug users than other approaches to personality asse
ssment. A problem in diagnosis is separating behaviours inherent in th
e activity of drug misuse from true evidence of PD, especially the ant
i-social type (ASPD), and rating instruments vary in their ability to
do this. Nevertheless, the available evidence suggests that approximat
ely two-thirds of drug users in treatment have PD, with ASPD the most
common. Studies have mainly been in opiate users, while the prevalence
of PD may be lower across the range of drugs, and in non-treatment se
ttings. PD has been found to be associated with a range of complicatio
ns and adverse outcomes in drug use, including psychiatric problems, p
oor social functioning, dropout from treatment, and increased HIV risk
behaviours and infection rates. Outcomes for ASPD individuals in meth
adone maintenance treatment appear reasonable, however, and it may be
that early recourse to such treatment is the most practical option for
many PD opiate users, a potential criticism being that this does not
directly address the PD problems.