Mental health problems: Are they or are they not a risk factor for dropout from drug treatment? A systematic review of the evidence

Background: A sizeable number of recent studies investigating whether clients with substance misuse and mental health problems (dual diagnosis clients) are at heightened risk of dropout from drug treatment have been published. It is timely that their findings are brought together in a comprehensive review of the current evidence. Aims: The aim of the review is to examine whether dually diagnosed clients are less likely to be retained in drug treatment than clients without mental health problems, and, if so, whether this varies for clients diagnosed with different types of mental health problems. Methods: The review considers peer-reviewed research published after 1 January 1990, which was located using the literature databases Medline and PsycInfo. Predefined search terms were used. Further papers were identified from the bibliographies of relevant publications. Findings: 58 studies (84% from the USA) met the inclusion criteria for the review. The findings suggest that for most clients, having a past history of mental health problems does not influence the likelihood of being retained in drug treatment. The body of evidence regarding concurrent mental health problems is contradictory. On the whole, the majority of studies suggest that neither presence nor severity of depressive, anxiety, or other Axis-I disorders is related to retention, but these findings are not entirely unequivocal, as a few studies report strong positive or negative associations between depression and anxiety disorders and retention. Few researchers looked separately at psychotic spectrum disorders hence no conclusions could be drawn. The presence of most personality disorders also did not appear to affect treatment tenure, with the exception of antisocial personality disorder, for which the evidence points towards a greater risk of dropout. Conclusions: The balance of evidence suggests that, overall, dual diagnosis clients with Axis-I disorders who seek treatment in drug treatment services are retained as well as clients without dual diagnosis. Subgroups of clients who appear more vulnerable to premature dropout include those with antisocial personality disorder. Methodological shortcomings of the reviewed studies and resulting implications for this review and future research are discussed