Incidence of psychoses among drug dependent patients in primary care with no psychiatric history: a retrospective observational matched-cohort study

Frisher, Martin; Martino, Orsolina I.; Bashford, James; Crome, Ilana; Croft, Peter

Abstract

Background and Objectives: While several studies have indicated a link between illicit drug use and the development of psychosis, the confounding role of pre-existing psychiatric illness is unclear. This study controls for this factor to a greater extent than has hitherto been possible, using a retrospective observational matched-cohort design controlling for age, gender, socioeconomic status and prior psychiatric illness.
Methods: 592 cases (diagnosed with drug misuse/dependence) and 592 controls (no recorded history of drug misuse/dependence) were drawn from all patients aged 16-44 in 183 practices within the General Practice Research Database (UK). On study entry, cases and controls had never had a psychiatric diagnosis since registering with their practice. The average look-back period was 17.7 years. The main outcome measure was diagnosis of psychosis (including schizophrenia) from study entry onwards.
Results: Patients with a drug misuse/dependence diagnosis are significantly more likely to be diagnosed with psychosis than those with no drug misuse/dependence history (RR = 2.10, 95% C.I. = 1.23-3.59) with the relative risk increasing as the definition of psychosis gets narrower.
Conclusions: This study has established that, when the confounding presence of previous psychiatric illness is removed, the onset of problematic substance misuse severe enough to warrant primary care consultation is a risk factor for future onset of first-ever psychotic illness. Thus, there is a distinct sub-group of psychotic patients among whom drug misuse/dependence, with no prior psychiatric illness, is a risk factor for the development of psychoses.

Citation

Frisher, M., Martino, O. I., Bashford, J., Crome, I., & Croft, P. (in press). Incidence of psychoses among drug dependent patients in primary care with no psychiatric history: a retrospective observational matched-cohort study. The European Journal of Psychiatry, 27(4), 240-247. https://doi.org/10.4321/s0213-61632013000400002

• Journal Article Type: Article
• Acceptance Date: Jan 1, 2013
• Deposit Date: Jun 12, 2023
• Journal: The European Journal of Psychiatry
• Print ISSN: 0213-6163
• Publisher: Elsevier
• Peer Reviewed: Peer Reviewed
• Volume: 27
• Issue: 4
• Pages: 240-247
• DOI: https://doi.org/10.4321/s0213-61632013000400002
• Keywords: Psychiatry and Mental health