The association between substance misuse and first-episode psychosis in a defined UK geographical area during the 1990s

OBJECTIVE: The aim of this study was to examine the prevalence of all substance use disorders (SUD) and cannabis-specific SUDs reported in two first-episode epidemiological studies, conducted in the same catchment area, 5 years apart.

METHODS: The prevalence of schizophrenia in Nottingham and Aetiology and Ethnicity of Schizophrenia and Other Psychoses studies included all people with a first-episode of psychosis between 1992 and 1994 and 1997 and 1999, respectively. Those individuals with a comorbid diagnosis of a SUD (ICD-10 harmful use or dependence) were identified.

RESULTS: An upward (but not statistically significant) trend in all SUDs was found for the first-episode study population as a whole, between the two cohorts (11.9-18.2%). When analysed by age, a significant increase in cannabis-specific SUDs was observed for all first-episode cases aged 16-29 between cohorts (3.2-10.6%). When analysed by age and gender, a significant increase in all SUDs was apparent for female first-episode patients aged 16-29 between cohorts (6.1-24.2%), this same increase was not seen in male patients.

CONCLUSIONS: Illegal drug misuse is common in patients with a first-episode of psychosis. However, most concerning is that when both age and gender are considered, females with a first-episode of psychosis aged 16-29 show a highly significant rise in the prevalence of all SUDs over the 1990s. More recent drug use data from England and Wales shows that the prevalence of drug use in the 21st century is declining; further epidemiological studies are required to determine whether this is also the case in young female first-episode psychosis populations.