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The Capital Region of Denmark - a part of Copenhagen University Hospital

Schizophrenia is associated with increased risk of subsequent substance abuse diagnosis - A Nationwide Population Based Register Study

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AIMS: We aimed to investigate whether a diagnosis of schizophrenia increases the risk of a substance abuse diagnosis.

DESIGN: Prospective cohort study using a longitudinal study design.

SETTING AND PARTICIPANTS: Individuals born in Denmark from 1955-1999 and registered in the Danish registers between Jan 1, 1968, and July 1, 2013.

MEASUREMENTS: We investigated the associations between schizophrenia and ICD diagnoses of substance abuse, both established through various Danish registers. The Cox regression model was used and adjusted for calendar year, gender, urbanicity, co-abuse, other psychiatric diagnoses, parents' substance abuse and psychiatric history, parents' immigration, and parents' socioeconomic position. Individuals diagnosed with substance abuse less than a year after diagnosis of schizophrenia were classified as not diagnosed with schizophrenia.

FINDINGS: The cohort consisted of 3,133,968 persons. During follow up (103,212,328 person-years at risk), a total of 14,007 individuals developed schizophrenia, with 2,885 subsequently diagnosed with substance abuse. A diagnosis of schizophrenia was positively associated with the risk of developing substance abuse (hazard ratio (HR) 3.69; 95% confidence interval (CI) 3.56-3.83). Additionally adjusting for a co-abuse markedly affected the associations, making schizophrenia primarily associated with an increased risk of abuse of cannabis, alcohol, stimulants, and other substances (adjusted HR 2.48; 95% CI 2.34-2.64 for cannabis - 1.94; 1.87-2.02 for alcohol - 1.77; 1.61-1.95 for stimulants - 1.36; 1.20-1.54 for other substances). The association was still significant 10-15 years subsequent a diagnosis of schizophrenia (HR 2.50; 95% CI 2.26-2.76).

CONCLUSIONS: In Denmark a diagnosis of schizophrenia is significantly associated with increased risk of subsequent diagnosis of substance abuse.

Original languageEnglish
JournalAddiction (Abingdon, England)
Pages (from-to)2217-2226
Publication statusPublished - Dec 2019

ID: 57628092