title: Prognosis of schizophrenia in persons with and without a history of cannabis use.
abstract: BACKGROUND
  The aim of the study was to determinate whether schizophrenia patients with a history of cannabis use have a different prognosis, with regards to readmission and hospital duration, compared with those without a history of cannabis use.
  
  
  METHODS
  The present investigation was a cohort study of 50,087 Swedish men with data on cannabis use at the ages of 18-20 years. A total of 357 cases of schizophrenia were identified from in-patient care and followed up from 1973 to 2007.
  
  
  RESULTS
  Schizophrenia patients with a history of cannabis use had a higher median duration of first hospital episode (59 days v. 30 days). Patients with a history of cannabis use had a higher median rate of readmission (10 times v. four times). Also, total number of hospital days was higher in patients with a history of cannabis use compared with those without (547 days v. 184 days). Patients with a history of cannabis use had an increased odds of having more than 20 hospital readmissions compared with non-users [3.1, 95% confidence interval (CI) 1.3-7.3] as well as an increased odds of hospital admission lasting more than 2 years (2.4, 95% CI 1.1-7.4) after controlling for diagnosis of personality disorders, family socio-economic position, IQ score, civil status, place of residence, risky use of alcohol and use of other drugs. Patients with a history of cannabis use were less likely to have paranoid schizophrenia compared with never users (8% v. 17%) in the first admission.
  
  
  CONCLUSIONS
  Schizophrenia patients with a history of cannabis use had a significantly higher burden of lifetime in-patient care than non-cannabis users. Not only does cannabis increase the risk of schizophrenia, but also our findings indicate that the course and prognosis of schizophrenia may be more severe than schizophrenia cases in general.
authors: Department of Public Health Sciences, Division of Social Medicine,Karolinska Institutet,Stockholm,Sweden.
authors: E
authors: E
authors: Manrique-Garcia
authors: Department of Psychological Medicine and Neurology, MRC Centre for Neuropsychiatric Genetics and Genomics,Cardiff University,Cardiff,UK.
authors: S
authors: S
authors: Zammit
authors: Department of Public Health Sciences, Division of Public Health Epidemiology,Karolinska Institutet,Stockholm,Sweden.
authors: C
authors: C
authors: Dalman
authors: Institute of Environmental Medicine,Karolinska Institutet,Stockholm,Sweden.
authors: T
authors: T
authors: Hemmingsson
authors: Department of Public Health Sciences, Division of Social Medicine,Karolinska Institutet,Stockholm,Sweden.
authors: S
authors: S
authors: Andreasson
authors: Department of Public Health Sciences, Division of Social Medicine,Karolinska Institutet,Stockholm,Sweden.
authors: P
authors: P
authors: Allebeck
mesh_terms: D002188:Cannabis / Q000009:adverse effects*; D005500:Follow-Up Studies; D006760:Hospitalization / Q000706:statistics & numerical data*; D006801:Humans; D007902:Length of Stay / Q000706:statistics & numerical data; D008297:Male; D008875:Middle Aged; D010359:Patient Readmission / Q000706:statistics & numerical data; D011379:Prognosis; D012559:Schizophrenia / Q000139:chemically induced / Q000453:epidemiology* / Q000628:therapy; D013548:Sweden / Q000453:epidemiology