According to a report by the WSJ, the percentage of working Americans testing positive for drugs hit a two-decade high last year, driven by an increase in positive marijuana tests, as businesses might have loosened screening policies amid nationwide labor shortages.

Of the more than six million general workforce urine tests that Quest Diagnostics Inc., one of the country’s largest drug-testing laboratories, screened for marijuana last year, 3.9% came back positive, an increase of more than 8% from 2020, according to Quest’s annual drug-testing index.

That figure is up 50% since 2017. Since then, the number of states that legalized marijuana for recreational use grew to 18 from eight, plus the District of Columbia.

Despite the increase in positivity last year, fewer companies tested their employees for THC, the substance in marijuana primarily responsible for its effects, than in recent years, said Barry Sample, Quest’s senior science consultant.

The shifting legal backdrop and changing cultural attitudes have prompted some employers to stop testing for marijuana while companies in some states are barred from factoring the test results into hiring decisions, according to Dr. Sample. And those trends accelerated last year amid the recent shortage of workers, especially in states where recreational marijuana is legal, Dr. Sample added.

The percentage of specimens tested for THC declined 6.7% nationwide in 2021 from 2020, while that figure fell by 10.3% in states where recreational marijuana is legal, according to Quest’s data.

Overall, the proportion of U.S. workers who tested positive for the various drugs Quest screened for in 2021 rose to 4.6%, the highest level since 2001, according to Quest, which analyzed nearly nine million overall urine tests last year on behalf of employers.That percentage is more than 31% higher than the low of 3.5% a decade ago, in the early days of a resurgent heroin epidemic in the U.S.

In the hospitality industry, many employers stopped screening potential employees for drugs, including marijuana, before the pandemic, according to one representative for a hotel management company with operations across the country, including in Georgia, Minnesota and Colorado.

The representative said their company along with several of their industry peers stopped conducting pre-employment drug tests in the past five years because of the associated expenses and evolving legal landscape.

Chris Layden, senior vice president at staffing firm ManpowerGroup, said the elimination of marijuana screening is one of the most common ways companies are seeking to expand their pool of eligible workers. ManpowerGroup estimated that drug testing eliminates about 5% of candidates.

ManpowerGroup is seeing companies across nearly all industries, except for financial services and federally regulated businesses, eliminate marijuana testing requirements, Mr. Layden said.

Michelle Bearden, chief risk and operating officer for Houston-based staffing and recruiting firm Link Staffing Services Inc., said she has yet to see a strong reason why Link Staffing should move to loosen pre-employment marijuana screenings before the federal government does. She acknowledged the job market has been tight during the pandemic, but said she doesn’t think nixing THC screenings is a good solution.

In Texas, Link Staffing, which mostly hires for the manufacturing and distribution sectors in the Dallas and Houston areas, has made some concessions to fill open roles amid the labor shortage, including by easing background-check requirements, Ms. Bearden said. And while it can still be tough to fill open roles, Link Staffing and the employers it works with still view marijuana use as a deal breaker.