Comorbid mental disorders and substance use disorders: epidemiology, prevention and treatment

Introduction to the chapters in the monograph

Page last updated: 2003

The definitional issues surrounding comorbidity are in no way trivial. Degenhardt (Australia), Hall (Australia) and Lynskey (USA) provide a discussion of the definitional and methodological issues in the study of comorbidity in the second chapter. Chapter 2 outlines the development of psychiatric diagnostic systems; the definition of what is meant by comorbidity; theories on the causes of comorbidity; and an outline of why comorbidity is important.

Chapter 3 by Andrews, Issakidis & Slade (Australia) is built on the strengths of recent national epidemiological studies in the USA, Australia, The Netherlands and Canada. The authors, from the WHO Research and Training Centre in Mental Health and Substance Abuse, provide an analysis of 'How common is comorbidity?' from a whole of population perspective. Most studies examining substance use and mental disorder comorbidity are in treatment settings. These studies provide valuable clinical information for the best estimates of comorbidity for individuals who are receiving treatment for at least one disorder. However, they overestimate the true level of comorbidity in the population because people with comorbid disorders are more likely to seek treatment simply because they have more disorders (Berkson's bias). An analysis of associated burden and unmet need and comorbidity are addressed in this chapter.

Prevention is a crucial component in the breadth of interventions considered in the area of comorbidity. Dadds and Atkinson (Australia) provide a critical analysis of prevention in Chapter 4. The prevention of mental disorders has a low priority in the health care agendas of most countries. The Chapter outlines the substantial growth in the knowledge about both environmental and genetic risk factors for mental disorders and substance use disorders. Secondly, a number of promising models for early intervention now exist and are reviewed.

The treatment research is reviewed by Kavanagh (Australia), Mueser (USA) and Baker (Australia) in Chapter 5, and the service delivery implications in Chapter 6 by Proudfoot (Australia),Teesson (Australia), Brewin (UK) and Gournay (UK). The chapter by Kavanagh and colleagues addresses the treatment implications of comorbidity, including the finding that comorbidity is more common in treatment samples than in the general population; assessment issues; evidence for the effectiveness of treatment interventions in persons with comorbid mental health and substance use disorders; and evidence as to whether the presence of comorbidity influences treatment outcomes. Chapter 6 reviews the evidence for service delivery structures and provides a discussion of the organisation of services and the extent to which current service organisation and funding systems address comorbidity. Finally, Chapter 7 by Manns provides the crucial consumer point of view that is often overlooked in research on best practice for mental illness.