The retired athlete, who is married to German tennis champ Steffi Graf, confesses he regularly used the drug to get high in the late 1990s in his new memoir Open.
He tells People.com, "I can't speak to addiction, but a lot of people would say that if you're using anything as an escape, you have a problem."
And he admits he initially worried about what his fans would think about his drug confession: "I was worried for a moment, but not for long... I was actually excited about telling the world the whole story."