Actor Bradley Cooper has revealed his life was once just as wild as that of his boozy "The Hangover" character - and he smashed his head open during one crazy night out in his 20s.

The star insists he's now clean and sober and hasn't touched alcohol or drugs since he was 29.

And it took a very stupid act for him to straighten up.

He tells The Hollywood Reporter, "I was at a party, and deliberately bashed my head on the concrete floor, like, 'Hey, look how tough I am!' I did it again (and) I spent the night at St. Vincent's Hospital with a sock of ice, waiting for them to stitch me up."

And now 37, Cooper admits he's glad he turned his back on his wild past: "I don't drink or do drugs anymore... Being sober helps a great deal... I remember looking at my life, my apartment... and I thought, 'What's happening?'"

"I realized I wasn't going to live up to my potential, and that scared the hell out of me. I thought, 'Wow, I'm actually gonna ruin my life. I'm really gonna ruin it.'"