According to the report, Johnson failed three drug tests -- two for cocaine in 2012 and this year, and one for marijuana in 2009.
Johnson, 30, was reportedly suspended for the 2012 failed test, but it was never made public. The PGA Tour is not required to announce any disciplinary actions against players who test positive for recreational drugs.
Johnson announced Thursday that he was taking a leave of absence from golf.
"I will use this time to seek professional help for personal challenges I have faced," he said in a statement. "By committing the time and resources necessary to improve my mental health, physical well-being and emotional foundation, I am confident that I will be better equipped to fulfill my potential and become a consistent champion."
The PGA Tour released a statement on Thursday that read: "We have nothing to add to Dustin's statements but wish him well and look forward to his return to the PGA Tour in the future."
Executive vice president of the PGA Tour, Ty Votaw, said there would be no further comment.
Johnson attributed a previous absence from golf to a back injury. Golf.com reported that Johnson was serving a suspension for failing a drug test for cocaine. At the time, the PGA Tour did not comment and Johnson's agent denied that he was suspended.Copyright © 2015, The Baltimore Sun