Actor Zac Efron reportedly completed a secret stint in rehab about five months ago for cocaine addiction. While statistically cocaine is one of the least used drugs among young adults, it seems to be the drug of choice among celebrities.

"Cocaine is unique in how it stimulates the brain’s reward center. The chemical signal for pleasure in the brain is the release of dopamine in the nucleus accumbens in the midbrain," explained Dr. David Sack, CEO of Malibu rehab center Promises. "Cocaine strongly and selectively increases dopamine in this region, causing the ‘rush’ and euphoria."

Efron, 25, is reportedly clean and sober after a battle with cocaine addiction and dabbling with the popular party drug “Molly.” According to TMZ, Efron’s problem spiraled out of control while he was filming the movie Neighbors, which was shot in April.

“We're told ... early this year, Zac and some friends went on a coke rager in a room at the SkyLofts at the MGM Grand in Vegas ... and caused around $50k in damage,” wrote TMZ. “No word on who took care of the bill.”

On the red carpet at Toronto International Film Festival, Efron and his reps seemed determined to focus on his career.

"He's healthy, happy and not drinking," E! Online quoted an unnamed source as saying. "He's taking time to focus on working."

But Efron isn’t the only star who has allegedly battled drug addiction. Charlie Sheen, Paris Hilton, Amy Winehouse, Bruno Mars, and Lamar Odom have all been accused of using cocaine. According to a piece on Fox News, cocaine is as commonplace as a glass of wine among the Hollywood elite. Actor Dennis Quaid said he became addicted to cocaine at the beginning of his career because it was easy to purchase and always around.

"It was very casual at first. That's what people were doing when they were at parties. Cocaine was even in the budgets of movies, thinly disguised," Quaid said. "It was petty cash, you know? It was supplied, basically, on movie sets because everyone was doing it. People would make deals. Instead of having a cocktail, you'd have a line."

Dr. Reef Karim, a leading addiction specialist at The Control Center in Los Angeles, echoed Quaid’s sentiments, saying that while cocaine dependence is not a big thing among the general public, it’s still a big problem among some of the world’s biggest stars.

"In general, with cocaine abuse, or cocaine dependence, the numbers are dropping. They are not peaking or elevating. But in Hollywood, it’s still going strong," said Karim. "You still see coke everywhere in Hollywood. It is still considered to be a party drug."

Luckily for Efron, he received treatment and seems to be doing a lot better.

“I’m good, real good,” he said.