Former members of Chris Brown's inner circle lay bare his issues with drugs and controlling his anger...
The article is extensive but here's small a small part explaining his drug use.
From Billboard Magazine
...At this time, Brown was preparing for the European leg of his One Hell of a Nite Tour, but, according to various members of his team at the time, he would stay up for as long as three days in a row, snorting cocaine and dabbling in Xanax, marijuana, Molly and lean.
…. “He will cuss you out and say, ‘Hey, man, I’m functioning. I’m going to get the work out.’ And he does,” says a current member of Brown’s team. “But [he’s not] the first functional star who thinks they can handle those powerful drugs. I got to say with all my heart, he’s dancing with death.”The article also talks about his fractured relationship with his mother and his incessant need to cyber stalk Karrueche Tran.
Chris denies the claims.