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Article
November 28, 1990

The Efficacy of Preemployment Drug Screening for Marijuana and Cocaine in Predicting Employment Outcome

Author Affiliations

From the Boston Postal Service Medical Unit (Drs Zwerling and Ryan), the Occupational Medicine Program, Department of Environmental Science and Physiology, Harvard School of Public Health (Drs Zwerling and Ryan), the Occupational Medicine Clinic, Massachusetts General Hospital (Dr Zwerling), the Department of Community Medicine, Tufts University School of Medicine (Dr Ryan), and the Department Of Biostatistics, Harvard School of Public Health (Dr Orav), Boston, Mass. Dr Zwerling is now with the Institute of Agricultural Medicine and Occupational Health, Department of Preventive Medicine and Environmental Health, College of Medicine, Oakdale Campus, University of Iowa, Iowa City.

From the Boston Postal Service Medical Unit (Drs Zwerling and Ryan), the Occupational Medicine Program, Department of Environmental Science and Physiology, Harvard School of Public Health (Drs Zwerling and Ryan), the Occupational Medicine Clinic, Massachusetts General Hospital (Dr Zwerling), the Department of Community Medicine, Tufts University School of Medicine (Dr Ryan), and the Department Of Biostatistics, Harvard School of Public Health (Dr Orav), Boston, Mass. Dr Zwerling is now with the Institute of Agricultural Medicine and Occupational Health, Department of Preventive Medicine and Environmental Health, College of Medicine, Oakdale Campus, University of Iowa, Iowa City.

JAMA. 1990;264(20):2639-2643. doi:10.1001/jama.1990.03450200047029
Abstract

We present a prospective, controlled study of the association between preemployment drug screening results and employment outcomes in 2537 postal employees. For identified marijuana users, relative risk for turnover was 1.56 (95% confidence interval [CI], 1.17 to 2.08); accidents, 1.55 (95% CI, 1.16 to 2.08); injuries, 1.85 (95% CI, 1.30 to 2.64); and discipline, 1.55 (95% CI, 1.03 to 2.32). Their mean absence rate was 7.1% compared with 4.0% for nonusers. For identified cocaine users, relative risk for turnover was 1.15 (95% CI, 0.65 to 2.05); accidents, 1.59 (95% CI, 0.95 to 2.67); injuries, 1.85 (95% CI, 1.01 to 3.39); and discipline, 1.40 (95% CI, 0.62 to 3.17). Their mean absence rate was 9.8%. Our study shows that a preemployment drug screen positive for marijuana or cocaine is associated with adverse employment outcomes. The level of risk, however, is much less than previously estimated. This finding has important implications for the social, legal, and economic arguments for and against drug testing.

(JAMA. 1990;264:2639-2643)

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