American actor Matthew McConaughey disclosed in his new memoir that he was sexually abused when he was a teenager.

In Greenlights, which was released on Tuesday (Oct 20), the 50-year-old actor lists several moments in his life and career as either green, yellow or red lights - similar to the colour code on traffic lights. These events either caused him to advance, pause or stop, according to Variety magazine.

He begins his memoir by sharing facts about himself, including several disturbing incidents of sexual abuse.

"I was blackmailed into having sex for the first time when I was 15," the Oscar-winning actor of Dallas Buyers Club (2013) writes in his autobiography.

"I was certain I was going to hell for the premarital sex. Today, I am merely certain that I hope that's not the case."

McConaughey also mentions another incident in the book, when he was molested by a man when he was 18 "while knocked unconscious in the back of a van".

He does not reveal further details on both incidents in the book, but says he does not consider himself a victim of the situations.

"I've never felt like a victim," he writes. "I have a lot of proof that the world is conspiring to make me happy," he says.

Known for starring in romantic comedies such as The Wedding Planner (2001), How To Lose A Guy In 10 Days (2003) and Ghosts Of Girlfriends Past (2009), the actor recounts in the book how he landed his breakthrough role in the coming-of-age comedy film Dazed And Confused (1993) and his first leading role in the 1996 film adaptation of John Grisham's legal novel A Time To Kill.

Married to model and designer Camila Alves with three children, he also writes about his parents' stormy relationship, his marriage and his personal philosophy in the memoir.