Marijuana and workplace safety: an examination of urine drug tests

J Addict Dis. 2014;33(1):24-7. doi: 10.1080/10550887.2014.882729.


Although the decriminalization of recreational marijuana and medical marijuana laws provide a compassionate answer for treatment-related issues in patients' lives, they leave questions open as to the impact on other realms of life, such as employment and safety. This is a case-control study comparing the proportion of marijuana positive urine specimens for post-accident verses random samples. The marijuana concentration of each sample underwent creatinine normalization to account for in vivo dilution. Any sample that tested positive for one or more substances other than marijuana was eliminated from the study. The prevalence of marijuana violations, the odds ratio and 95% confidence interval of accident involvement and the population attributable risk were calculated. A two-by-two table was created with the remaining data and the data were used to calculate the odds ratio, resulting in a value of 0.814 with a 95% confidence interval between 0.625 and 1.060. The Fisher exact probability test generated a 2-tailed P of .139. The subsequent population attributable risk was found to be -1.83%. These findings fail to reject the null hypothesis, and this study failed to demonstrate a statistically significant difference between the numbers of laboratory positive marijuana urine drug tests for a group of random drug tests compared with a group of post-accident drug tests.

Keywords: Marijuana; creatinine normalization; safety; urine drug testing.

MeSH terms

  • Accidents, Occupational / statistics & numerical data*
  • Case-Control Studies
  • Confidence Intervals
  • Creatinine / urine
  • Dose-Response Relationship, Drug
  • Humans
  • Marijuana Abuse / epidemiology
  • Marijuana Abuse / urine*
  • Occupational Health*
  • Prevalence
  • Probability
  • Substance Abuse Detection / methods*
  • United States / epidemiology
  • Workplace / statistics & numerical data


  • Creatinine