Psychosis and substance abuse: cause, effect or coincidence?

An association between substance abuse and major psychiatric illness is increasingly well recognised, but most studies have been conducted in the USA and have focussed upon patients with schizophrenia rather than other disorders. We conducted a survey of 38 consecutively admitted patients with DSM-III-R functional psychoses. A semi-structured substance abuse interview was administered and a urine specimen for drug metabolite screening requested. The prevalence of cigarette smoking (63%) and current illicit drug use (26%) were higher than general population norms. The 16 subjects with schizophrenia and related disorders were more likely to smoke cigarettes than the 22 patients with an affective disorder (p = 0.008, odds ratio 8.4, 95% Cl 1.3-69.6), and showed tendencies to more illicit drug and alcohol consumption. Illicit drug users were more likely to have a forensic history and less likely to have entered further education. Substance abuse is common among patients with psychoses, particularly in those with schizophrenia and related disorders. All psychotic patients should have a detailed drug history taken, and therapeutic attempts made to reduce consumption.