Substance misuse and early psychosis.

Objective: This paper sought to review current knowledge about the relationship between substance misuse and early psychosis. Methods: A literature search was conducted using Medline and restricting the search to articles after 1996. Additional articles were sourced from reference lists of relevant articles. Results: There is a high prevalence of substance misuse among persons with early psychosis, with cannabis and alcohol featuring prominently. Substance misuse is associated with earlier onset and possibly more positive symptoms, although apparently not with greater cognitive impairment. Cannabis appears to confer an increased likelihood of developing schizophrenia in biologically vulnerable individuals. Amphetamines also cause psychosis which may become chronic, although specific vulnerability to this effect is less well established. Many cases of so-called 'drug-induced psychosis' become diagnosed as schizophrenia in later years. Specific intervention programs report positive outcomes with regard to substance misuse and the course of psychosis. Conclusions: Substance misuse should always be assessed in this patient group, bearing in mind the potential interactive causes of psychopathology. Intervention is of value in improving outcomes.