Study Finds Drug Test Value Exaggerated : Employment: As expected, workers who tested positive before hiring have more injuries and absences. But the rates are far lower than earlier estimates.
People who test positive on pre-employment drug screening are more likely to have work-related problems than those who test negative, but the benefits of the controversial screening programs have been exaggerated, according to a study of 2,537 Boston postal workers published in today’s Journal of the American Medical Assn.
Researchers found “an association” between a positive drug test for marijuana or cocaine and problems such as industrial accidents, injuries and absenteeism, but the relationship “is more modest than what people seem to want to hear,” said Dr. Craig Zwerling of the University of Iowa. Zwerling, the principal author of the study, previously worked as a physician for the U.S. Postal Service in Boston.
Others said the figures in the report are substantial and support the need for pre-employment drug screening.
The researchers found that the 7.8% of postal employees with marijuana-positive urine samples had 55% more industrial accidents and 78% more absences when compared to other employees. The 2.2% of postal employees with cocaine-positive urine samples had 145% more absences and 85% more injuries.
According to the report, these percentages are far lower than earlier estimates, publicized in scientific journals in the mid-1980s, that workers who use drugs are involved in 200% to 300% more industrial accidents, sustain 400% more compensable injuries and use 1,500% more sick leave than workers who do not use drugs.
This led the researchers to conclude that “many of the claims cited to justify pre-employment drug screening have been exaggerated.”
“It seems a little ludicrous to me that we spend loads of money to find the marijuana user in the employee population and we largely ignore the serious drug abuse problem in the criminal population,” said Eric D. Wish, a substance-abuse researcher at the University of Maryland. Wish wrote an editorial for the medical journal on the study.
Others took a different view.
“Even if you take the lowest numbers, they are still significant,” said Jonathan Segal, a management attorney with Wolf, Block, Schorr & Solis-Cohen in Philadelphia.
The numbers “are substantial,” said Joel S. Trosch, an assistant postmaster general. “The results of the study support (pre-employment) drug screening” by the Postal Service.
Over the last several years, an increasing number of companies, including The Times, have established mandatory pre-employment drug screening programs. Typically, job applicants who test positive for drugs without a valid medical reason are not hired.
The new study is one of the first to scrutinize the effectiveness of the practice. The researchers note that earlier estimates of the problems caused by drug-abusing employees were not based on solid data.
The study, conducted between 1986 and 1989, was a “blind study,” which means employees, hiring officials, medical personnel and management officials were not informed of the results of the urine drug screens and the test results had no effect on hiring decisions. The Postal Service has since instituted a national policy of pre-employment screening.
In the study, urine drug screens were performed on nearly 5,000 applicants for postal jobs. Positive tests were confirmed by additional testing.
The work performance of individuals who were hired, including absence rate, work-related injuries and accidents, disciplinary actions and terminations, were followed for an average of 406 days.
“Those with marijuana-positive urine samples had increased risks of termination, accidents, injuries and discipline compared with those with negative urine samples,” the report said. The results for those with cocaine-positive urine samples were similar, except that these individuals were not at increased risk of being fired.
The Postal Service has subsequently confirmed these findings in tests conducted at 21 sites around the country, a spokesman said.
A key shortcoming of the study is that it did not take into account the possible role of alcohol abuse, in addition to drug use, in poor work performance. The researchers did not perform blood or urine tests that might have detected alcohol abuse. They also did not ask job applicants about alcohol because they thought the applicants were unlikely for give accurate information.
Zwerling said the study was not meant to tell companies whether to perform pre-employment drug screening, but to “provide an empirical background” for discussions.
Segal, the management attorney, said that as more employers establish testing programs, companies that do not test “run the risk of attracting a higher percentage of employees who use drugs. . . . Job applicants know which companies test and which don’t.”
