The most recent version of an annual report issued by Quest Diagnostics indicates that 4.4 percent of workplace drug tests in 2018 were positive for illicit drugs, an increase over the 4.2 percent positivity rate in 2017 and the highest rate since 2004. According to Quest, the increase was largely fueled by marijuana use. Across the U.S. work force, the percentage of drug tests that were positive for marijuana rose from 2.6 percent in 2017 to 2.8 percent in 2018.  The report also characterizes the results of drug tests of the federally mandated “safety-sensitive” work force, which comprises workers who are responsible for their own or other people’s safety. Among this population, the positivity rate for marijuana was 0.88 percent in 2018, a nearly five percent increase over 2017 and a 24 percent increase over 2014. In contrast to marijuana, the rate of opiate use is declining among U.S. workers. For the general work force, opiate positivity declined 21 percent between 2017 and 2018. Heroin and cocaine positivity rates also fell for both the general work force and the safety-sensitive work force. The report is available as a PDF. For more information, read Quest’s press release.