Donnie Wahlberg recently reflected on one of his earliest Hollywood roles in The Sixth Sense alongside the legendary Bruce Willis, and he shared that preparing for the role quite literally drove him to the brink of insanity.

The Blue Bloods actor starred in the classic horror film as Vincent Gray, the unhinged psychiatry patient who shoots Willis’ Malcome Crowe at the beginning of the story. The character is so emaciated and unkept that Wahlberg is nearly unrecognizable.

To prepare for the part, Donnie Wahlberg had to drop 47 pounds, quickly. The feat would have been highly painful and unhealthy for anyone. But it was especially taxing for someone like Wahlberg who had been a muscle-bound weightlifter at the time.

“I spent five weeks suffering and starving myself and doing all this stuff,” he explained to ET’s Nischelle Turner. “It was really hard, and it probably took me a year or two to get back to my right mind. Not that I was dangerous or anything, but what I went through to change physically, starving myself.”

Donnie Wahlberg Admits His ‘Sixth Sense’ Role Left Him with Lasting Issues

Donnie Wahlberg admitted that those few weeks of preparation created an underlying eating disorder that took him about two years to kick. Every time he sat down for a meal, his mind would click back to his extreme dieting, and he would tell himself “Oh, I can only eat this much,” and after his meal, he would head straight to the gym to burn it off.

“I just kind of wasn’t myself,” he continued. “I really went through such a transformation for that part that it was really difficult for me to come back.”

He, however, did take some positives away from The Sixth Sense, which is celebrating 25 years right now. And most of what he gained was from Bruce Willis, who proved to be an extremely encouraging, appreciative, and uplifting co-star.

“There are very few people in movie history who are cooler than Bruce,” he shared. “I remember when we went to the premiere of The Sixth Sense he just kept hugging me and saying, ‘You did so good. You did so good. You really helped the movie.’”

Wahlberg also recalled Willis involving him in the behind-the-scenes talks and how the actor had his back when Wahlberg was filming his emotionally strenuous scene.

“To be standing there that vulnerable for me in a scene like that, which was a really big moment in my career, you know, to be across from him and knowing he had my back, it meant the word to me,” he continued. “… Bruce was so supportive… He just had my back… It was a great thrill to work with him and to get to know him.”