Parts of this chapter are based on a paper currently under editorial review (Dawe, McKetin & Kingswell, unpublished).

There has been a growing acknowledgement that comorbid psychiatric and substance use disorders require careful assessment and treatment. For example, the Australian National Comorbidity Project has brought together for the first time both the National Drug Strategy and the National Mental Health Strategy with the aims of providing an opportunity for information sharing among key stakeholders working in comorbidity and identifying actions for progression of issues (Teesson & Burns, 2001).

There are now major epidemiological and clinical studies in which the prevalence of such comorbidity has been well documented for substance use disorders generally. There has, however, been considerable variability in the extent to which the relationship between individual substances or combinations of substances and mental health problems has been investigated.

Understandably, given the high rates of alcohol use across the western world, we know a great deal about comorbidity in people with alcohol use disorders. Although the use of amphetamines and other psychostimulants is increasing, there has been relatively less investigation of mental health problems in relation to this class of substances. In this chapter we have focused predominantly on amphetamines, the psychostimulant most widely used in Australia (Australian Institute of Health and Welfare, 2002a).

An overview of prevalence, clinical course, pharmacological management and possible psychosocial interventions is presented for both psychostimulant-induced psychosis and psychostimulant-induced mood and anxiety disorders. Issues related to the assessment of comorbid conditions are presented next. A range of assessment strategies is presented, including the use of diagnostic and screening instruments and measures of symptom severity. Finally, the emerging literature on psychosocial approaches to comorbidity is briefly presented.