title: Testing for cannabis in the work-place: a review of the evidence.
abstract: BACKGROUND
  Urinalysis testing in the work-place has been adopted widely by employers in the United States to deter employee drug use and promote 'drug-free' work-places. In other countries, such as Canada, testing is focused more narrowly on identifying employees whose drug use puts the safety of others at risk.
  
  
  OBJECTIVE
  We review 20 years of published literature on questions relevant to the objectives of work-place drug testing (WPDT), with a special emphasis on cannabis, the most commonly detected drug.
  
  
  RESULTS
  We conclude (i) that the acute effects of smoking cannabis impair performance for a period of about 4 hours; (ii) long-term heavy use of cannabis can impair cognitive ability, but it is not clear that heavy cannabis users represent a meaningful job safety risk unless using before work or on the job; (iii) urine tests have poor validity and low sensitivity to detect employees who represent a safety risk; (iv) drug testing is related to reductions in the prevalence of cannabis positive tests among employees, but this might not translate into fewer cannabis users; and (v) urinalysis has not been shown to have a meaningful impact on job injury/accident rates.
  
  
  CONCLUSIONS
  Urinalysis testing is not recommended as a diagnostic tool to identify employees who represent a job safety risk from cannabis use. Blood testing for active tetrahydrocannabinol (THC) can be considered by employers who wish to identify employees whose performance may be impaired by their cannabis use.
authors.affiliation: Centre for Addictions Research of BC and School of Health Information Science, University of Victoria, Victoria, BC V8W 2Y2, Canada. scottmac@uvic.ca
authors.forename: Scott
authors.initials: S
authors.lastname: Macdonald
authors.forename: Wayne
authors.initials: W
authors.lastname: Hall
authors.forename: Paul
authors.initials: P
authors.lastname: Roman
authors.forename: Tim
authors.initials: T
authors.lastname: Stockwell
authors.forename: Michelle
authors.initials: M
authors.lastname: Coghlan
authors.forename: Sverre
authors.initials: S
authors.lastname: Nesvaag
mesh_terms: D000056:Accident Prevention; D002188:Cannabis; D003071:Cognition / Q000187:drug effects*; D013759:Dronabinol / Q000097:blood / Q000652:urine; D006801:Humans; D012307:Risk Factors; D015813:Substance Abuse Detection / Q000379:methods*; D017132:Workplace
chemical_list: D013759:Dronabinol