Opioid abuse and hospitalization rates in patients with schizophrenia

Abstract

Background: Substance abuse worsens the course of schizophrenia, but it is not known whether or not there are differences between specific substances concerning their association with the hospitalizations of patients with schizophrenia. Aims: The primary aims of this study were to examine the possible associations between amphetamine, cannabis, and opioid abuse, and the risk of hospitalizations among patients with schizophrenia. Methods: The study population consisted of 146 patients with ICD-defined schizophrenia from two different geographical sites in Finland, and it included both inpatients and outpatients. Data were collected retrospectively from the patients’ medical files. Substance abuse was defined as either harmful use or dependence according to ICD-10. Results: The cumulative prevalence of substance abuse was 10.9% (16/146) for cannabis, 8.9% (13/146) for amphetamine, and 4.1% (6/146) for opioids. Among patients with schizophrenia and abuse of any substance, the number of hospitalizations was about 1.5-fold when compared to those without substance abuse. The incidence rate ratio for hospitalizations was 2.9 (95% CI 2.47–3.63) for opioids, 2.0 (1.71–2.41) for amphetamine, and 1.6 (1.33–1.84) for cannabis, when compared with no abuse of each substance. The risk of hospitalizations was significantly higher for opioids when compared with amphetamine (p < 0.001) or cannabis (p < 0.001). Conclusions: Harmful use or dependence of opioids among patients with schizophrenia is associated with significantly higher risk of hospitalizations than either harmful use or dependence of amphetamine or cannabis.

• Amphetamine
• Cannabis
• Hospitalization
• Opioid
• Schizophrenia

Declaration of interests: This study was supported by Ministry of Social Affairs and Health through the research fund for Niuvanniemi Hospital, Kuopio, Finland. The authors alone are responsible for the content and writing of the article. Kristiina Kivimies, Eila Repo-Tiihonen, Hannu Kautiainen, Paivi Maaranen and Leea Muhonen report no conflicts of interest. Martti Heikkinen is a member of an advisory board for Lundbeck, he reports receiving fees of clinical trials from Lundbeck, Shire, Forest, Takeda and Otsuka, support for travel to meetings from Lundbeck and Bristol- Myers-Squibb. Jari Tiihonen reports serving as a consultant to Lundbeck, Organon, Janssen-Cilag, Eli Lilly, AstraZeneca, F. Hoffman-La Roche, and Bristol-Myers Squibb. He has received fees for giving expert opinions to Bristol-Myers Squibb and GlaxoSmithKline and lecture fees from Janssen-Cilag, Bristol-Myers Squibb, Eli Lilly, Pfizer, Lundbeck, GlaxoSmithKline, AstraZeneca and Novartis. He is a member of advisory boards for AstraZeneca, Janssen-Cilag, and Otsuka.