By ERIC M. STRAUSS, JASMINE BROWN and ALEXA VALIENTE

Five years ago, when ABC News' "20/20? first met Rocco Decorso, the 12-year-old struggled to leave his house.

Every morning before school, Decorso refused to walk out the door, a routine activity for most school children. Decorso was paralyzed by fear about the dangers waiting outside.

Decorso was diagnosed with obsessive compulsive disorder at 8 years old. His parents said Decorso's fear of "What if?" consumed him.

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"I'll never forget going to a carnival. He was on a merry-go-round, crying," Margaret Decorso told "20/20? in 2009. "Like, you're supposed to have fun. Why is this kid crying?"

Decorso's father, John Decorso, told "20/20? that his young son started having suicidal thoughts. "Coming from a 6-year-old saying, 'I can't live like this. I want to live with God. Don't worry, Mommy and Daddy, I'll look down after you,' That's tough," he said.

In 2009, "20/20? embarked on a five-year journey with Rocco, who was on antidepressant medication and undergoing therapy to treat his OCD. At 12 years old, he still had a hard time leaving home, but he faced his fears and met up with ABC News' David Muir in New York City's Central Park to ride the merry-go-round.

"Each day felt like a month to me," Rocco said of his painful memories of having OCD.

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Today, Rocco, who is now 17 years old, said he is managing his OCD. He said he loves the freedom of driving and is looking forward to attending his junior prom. He plans to attend college in the future.

"I want to become a psychologist and help kids like I was," Rocco said recently. "Help that little Rocco-type guy. I could speak from experience."