title: Alcohol and cannabis use as risk factors for injury--a case-crossover analysis in a Swiss hospital emergency department.
abstract: BACKGROUND
  There is sufficient and consistent evidence that alcohol use is a causal risk factor for injury. For cannabis use, however, there is conflicting evidence; a detrimental dose-response effect of cannabis use on psychomotor and other relevant skills has been found in experimental laboratory studies, while a protective effect of cannabis use has also been found in epidemiological studies.
  
  
  METHODS
  Implementation of a case-crossover design study, with a representative sample of injured patients (N = 486; 332 men; 154 women) from the Emergency Department (ED) of the Lausanne University Hospital, which received treatment for different categories of injuries of varying aetiology.
  
  
  RESULTS
  Alcohol use in the six hours prior to injury was associated with a relative risk of 3.00 (C.I.: 1.78, 5.04) compared with no alcohol use, a dose-response relationship also was found. Cannabis use was inversely related to risk of injury (RR: 0.33; C.I.: 0.12, 0.92), also in a dose-response like manner. However, the sample size for people who had used cannabis was small. Simultaneous use of alcohol and cannabis did not show significantly elevated risk.
  
  
  CONCLUSIONS
  The most surprising result of our study was the inverse relationship between cannabis use and injury. Possible explanations and underlying mechanisms, such as use in safer environments or more compensatory behavior among cannabis users, were discussed.
authors.affiliation: Alcohol Treatment Center, Lausanne University Hospital, Lausanne, Switzerland. ggmel@sfa-ispa.ch
authors.forename: Gerhard
authors.initials: G
authors.lastname: Gmel
authors.forename: Hervé
authors.initials: H
authors.lastname: Kuendig
authors.forename: Jürgen
authors.initials: J
authors.lastname: Rehm
authors.forename: Nicolas
authors.initials: N
authors.lastname: Schreyer
authors.forename: Jean-Bernard
authors.initials: JB
authors.lastname: Daeppen
mesh_terms: D000328:Adult; D017677:Age Distribution; D000428:Alcohol Drinking / Q000009:adverse effects / Q000453:epidemiology*; D016022:Case-Control Studies; D018592:Cross-Over Studies; D004636:Emergency Service, Hospital / Q000706:statistics & numerical data*; D005260:Female; D005500:Follow-Up Studies; D006785:Hospitals, University; D006801:Humans; D015994:Incidence; D015601:Injury Severity Score; D008297:Male; D002189:Marijuana Abuse / Q000150:complications / Q000453:epidemiology*; D009104:Multiple Trauma / Q000175:diagnosis / Q000453:epidemiology; D012307:Risk Factors; D017678:Sex Distribution; D016019:Survival Analysis; D013557:Switzerland / Q000453:epidemiology; D014947:Wounds and Injuries / Q000453:epidemiology* / Q000209:etiology* / Q000503:physiopathology; D055815:Young Adult