"We applaud Jon for the courage he has shown in tackling this issue head on," the team said in a statement. "He has displayed a great deal of maturity and commitment over the past year and has the full support of the Astros organization. He is on the right track for his baseball career, and, more importantly, for his life. We are very proud of Jon."
Astros general manager Jeff Luhnow added that the team is behind Singleton in his struggle with addiction.
"It took a lot of courage for Jon to admit something like that publicly," Luhnow said. "Like we said in the statement, we stand behind him and believe it's an important step towards his recovery and hope that he has a great baseball career and puts this behind him."
Adam Karon, Singleton's agent, also showed his support for the slugger.
"We admire his courage and his candor and will support him 100 percent," Karon said. "The Astros have been great, been above and beyond, when it comes to their support."
Astros manager Bo Porter met with Singleton on Monday night after the team returned from a game in Jupiter, Fla., Luhnow said, and the team's support was communicated to him.
Singleton opened up to the AP about his past drug use, which he said began as a teenager growing up in Long Beach, Calif.
"At this point it's pretty evident to me that I'm a drug addict," he told the AP. "I don't openly tell everyone that, but it's pretty apparent to myself."
Singleton added: "I know that I enjoy smoking weed, I enjoy being high and I can't block that out of my mind that I enjoy that. So I have to work against that."
Singleton said his first positive test came in June 2012, and he quit using marijuana for the rest of the season. But he fell back into his old habits when he went to the Arizona Fall League that year and failed another drug test in December. That led to a one-month stay at an inpatient rehabilitation center.
"I knew I had a problem," he said. "Even after I failed the second drug test, I couldn't stop smoking weed. It was really bad. Me going there was definitely the best move."
After struggling on the field last year, Singleton said he turned to alcohol to battle anxiety and depression and was "waking up hung over every morning."
He said he's since cleaned up his life.
"I made up my mind to be my best, so hopefully better things happen because I'm not going out drinking and partying and doing all that kind of crazy stuff," he said.
Singleton, acquired from the Phillies in the blockbuster Hunter Pence deal in 2011, is on the 40-man roster and competing for a starting spot at first base, though he's likely to begin the season in the Minor Leagues.
Luhnow said the team is confident his troubles are in the past.
"I don't think he would have said it if he wasn't confident that he was well on the path to recovery," Luhnow said. "As anybody knows with any addiction, you're never fully recovered. It's always there in the background, but he's had a very good camp so far and we're encouraged by what we see, and we're fully supporting him.
"You can never absolutely say something is 100 percent behind you, but we're hopeful and optimistic that it is. Admitting it publicly is a big step and demonstrates he's serious about it."