"I have so much empathy for these young actors that are 19 and all of a sudden they're beautiful and famous and rich," he said in the interview. "I'm like, 'Oh my God, I'd be dead.'"
The actor said he kicked the habit for 23 years and remained sober until May 2013, when he briefly relapsed – after admitting to snorting heroin – and returned to rehab, spending 10 days in a detox program.
The second of four children, Hoffman was born on July 23, 1967 in Fairport, N.Y., to mother Marilyn O'Connor (née Loucks), a lawyer, and father Gordon Stowell Hoffman who worked for Xerox.
He graduated with a BFA in drama from New York University's Tisch School of the Arts in 1989 and began his film career in 1991, starring in his debut role in the indie production "Triple Bogey on a Par Five Hole."
Beyond movies, Hoffman also shined on Broadway, receiving two Tony nominations for Best Actor in 2000 for a revival of Sam Shepard's "True West" and again in 2003 for a revival of Eugene O'Neill's "Long Day's Journey into Night."
In 2012, Hoffman starred as Willy Loman in the Broadway revival of Arthur Miller's "Death of a Salesman," receiving rave reviews from critics and his third Tony Award nomination as Best Leading Actor in a Play.
He made his film directorial debut in 2010 with "Jack Goes Boating."
Hoffman's passing comes amid a flurry of new and upcoming projects. He appears in the 2014 movies "God's Pocket" and "A Most Wanted Man," along with "The Hunger Games: Mockingjay" Part 1 and 2, scheduled for release in the coming years.
He was also slated to star in the Showtime series, "Happyish."
Showtime executives released a statement Sunday, describing Hoffman was "one of our generation's finest and most brilliant actors."
Hoffman is survived by his girlfriend, costume designer Mimi O'Donnell, their son, Cooper, 10 and two daughters, Tallulah, 7, and Willa, 5.