8 - Dual diagnosis – drug misuse and psychiatric disorder

Summary

Introduction

One of the reasons why drug misuse is managed substantially as a psychiatric specialty is that it is strongly associated with various pervasive and clinically important psychiatric conditions. Studies have examined the relationship both ways round – that is, investigating rates of mental disorders in drug misusers, or the extent of drug misuse in mentally ill populations, and some of these are discussed here. In practice, clinicians must be skilled in recognizing personality disorder (often as a continuation of adolescent conduct disorder), depression, and anxiety states, all of which are extremely common and need to be distinguished from the effects of drug misuse itself. Personality disorder is particularly important, as it is often the main cause of abnormal mood in drug misusers and it exerts strong negative effects on many forms of treatment; the first part of the chapter focuses on this and the difficult area of drug-induced psychosis. The rest of the chapter is then given over to a discussion from the other perspective, of substance misuse problems in those with severe mental illness, as the rising rates of such problems are currently posing great difficulties in the provision of general psychiatric treatment in the community.

The management of those with schizophrenia and other psychotic conditions who misuse drugs is highly problematic, partly because such individuals do not comply well with conventional addiction treatment approaches, and a literature is emerging on ultra-specialist services for that group.