Dustin Johnson is taking a break from golf and will miss the Ryder Cup so he can tackle "personal challenges" in his life.
In a statement, the world number 16 said his leave of absence would start immediately but gave no indication on when he would return.
However, the 30-year-old's agent David Winkle told the PGA of America his client would not be in the field for the PGA Championship next week or the Ryder Cup in September.
In a statement from Hambric Sports Management, Johnson said: "I will use this time to seek professional help for personal challenges I have faced.
"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."
Johnson tied for fourth in the US Open in June and tied for 12th in the British Open earlier this month.
His decision will come as a blow to America's bid to reclaim the Ryder Cup, which this year takes place at Gleneagles in Scotland.
Johnson was almost certainly going to be included in captain Tom Watson's 12-man US team and had been highlighted as a potential weapon against Europe because of his length off the tee.
"We will certainly miss Dustin Johnson at Gleneagles, and we wish him the best," Watson said.
"As one of the longest hitters in the game with an undefeated record of 3-0 at Medinah in 2012, he has clearly been an asset for the United States team."