Drug screens deter employee drug use

Zero-tolerance policy discourage drug use

A report from the University of California, Irvine suggests that the reliance employers have on drug screening to deter drug use among employees is probably well-placed.

The results do not prove absolutely that drug testing reduces drug use, but are among the strongest indications yet, according to researcher Christopher Carpenter, PhD, a health economist at UC-Irvine's Merage School of Business.

Individuals whose employers perform drug tests are significantly less likely to report past month marijuana use, even after controlling for a wide array of worker and job characteristics, writes Carpenter. However, large negative associations were found for variables indicating whether a firm has drug education, an employee assistance program, or a simple written policy about substance use.

Frequent testing and severe penalties reduce the likelihood that workers use marijuana, the author concludes.

Link between testing and use overstated?

The Irvine study looked at cross-sections from the 2000-2001 National Household Surveys on Drug Abuse and the 2002 National Survey on Drug Use and Health. Among the possibilities Carpenter considered is whether healthier workers self-select workplaces that are more likely to screen employees. He also attempted to determine whether "zero tolerance" policies and employee assistance programs might influence worker drug use (and therefore lessen the association between testing and low drug use rates).

Carpenter found that policies like zero tolerance, as well as the characteristics of the workforce, influence worker drug use. He concludes that because past studies tended to not take those factors into account, they might have overstated the relationship between drug screens and drug use by up to 25%. Used together, frequent testing and severe penalties reduce the likelihood that workers use marijuana, he reports.


Christopher Carpenter, PhD, assistant professor of economics and public policy, Merage School of Business, University of California at Irvine. Email: kittc@uci.edu.

Carpenter CS. "Workplace drug testing and worker drug use." Health Services Research (online), 2006.