Spencer Pratt - whose sister Stephanie was arrested for DUI Oct. 18 - admits it's easy to get caught up in the wild Hollywood lifestyle.

"I mean, I've had problems with drinking in Hollywood, but who doesn't?" Pratt, 26, tells MTV News.

See how The Hills stars have changed over the years

He says when you're having fun, it's hard to realize that there's anything wrong. It also doesn't help when club promoters and bar-goers are "giving you unlimited high-end alcohol," he says.

"If you're out at a club every night having drinks, then you're drinking every night of the week," he says. "First, it starts off, 'Oh, I just love this dancing and having fun with friends.' But it's like, even though you're just having a couple of cocktails, [it adds up]."

See stars who've gone from wild to mild

Ironically, it is sister-in-law Holly Montag whose drinking is scrutinized on the current season of The Hills.

See Spencer Pratt and other stars who claim they've met their soul mates

He reveals that on an upcoming episode of The Hills, he and Heidi had to "step in."

Says Spencer, "Tune in — you'll see it when it clicks, when we're like, 'Yo, it's time to help Holly.'"

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