Background: There is little evidence contributing to the understanding of why people with schizophrenia and other psychotic illnesses use drugs and alcohol.
Method: A comprehensive literature search for evidence relevant to each of the following questions was undertaken, each of which is relevant to understanding why individuals with schizophrenia and other functional psychotic illnesses use drugs and alcohol: (1) Is substance misuse more prevalent among those with psychotic illness than the general Population? (2) Which problem generally develops first in dual diagnosis? (3) Can substance misuse cause schizophrenia and other functional psychotic illnesses? (4) Does dual diagnosis have a neurobiological Basis? (5) Is personality disorder a mediating factor in the relationship between psychotic illnesses and substance misuse? (6) Do individuals with psychotic illness use substances as self-medication? (7) Have changes in the care and social circumstances of people with psychotic illness, particularly deinstitutionalisation, led to a rise in substance misuse in this Population? (8) Do the social situations and social difficulties of people with psychotic illness lead to substance misuse? and (9) Do individuals with psychotic illness tend to begin using drugs and alcohol within mental health service settings or in the company of other users of such services?
Results: There is some evidence to support the idea that people with schizophrenia and other psychotic disorders use substances to reduce general dysphoria, and possibly negative symptoms. Social environment and experiences are also likely to be factors in the development of substance misuse in this group, but there is a dearth of empirical evidence.
Conclusions: There is a need for further research, especially concerning the social contexts of substance and alcohol misuse and the ways in which patterns of misuse develop among people with schizophrenia and other psychotic illnesses.