Zac Efron is running wild -- and opening up about his past struggles with addiction.
"The High School Musical" alum, 26, was the first celebrity to appear on "Running Wild with Bear Grylls," NBC's new reality show where Grylls takes celebrities on two-day excursions to put their survival skills to the test.
In addition to jumping out of a helicopter, being dropped into the Catskill Mountains, and eating a worm, Efron, who has completed two stints in rehab, opened up to the survivalist about achieving fame early on and what ultimately led to his struggles with addiction.
"It was just so quick -- it was shocking," the blue-eyed hunk admitted about hitting fame at such a young age. "The challenging part was never the work, that was never it," Efron began when asked by Grylls what led him to rehab. "It was sort of the in-between work -- the social aspects outside of it; everywhere you go [there are press and people watching] … and it can be confusing … and pretty soon you need a social lubricant," he said.
"Once it became that … it got to the point where I was caring less about the work and waiting more for the weekend where I couldn't wait to go out and let loose and have fun," the "Neighbors" actor went on. "But when Monday and Tuesday were difficult to get through, I thought, 'This is bad.'"
Although Efron is now able to open up about his struggles, he admits it's taken a lot to get to this point. "I just really never again want to take anything from the outside in to feel … comfortable in my present skin, and that takes a lot of work," he said. "It's just meditation and stopping and slowing down your brain."