By the time he joined the first cast of "Madtv" at the age of 27, he had developed a cocaine addiction. He wrote about the infamous "pig story" in which, dressed in full makeup and costume as a pig for a "Madtv" skit, he chased down his coke dealer and snorted so much cocaine that he nearly ruined the day's shoot.
Not long after, he wrote, he made his first serious attempt at suicide. Following a weekend coke binge, he wrote a final note to his mother and sister and swallowed 30 prescription sleeping pills and a pint of Jack Daniels. Crew members showed up at his apartment and rushed him to the hospital.
In and out of rehab and jail, Lange still managed to rack up the successes: getting standup gigs at all the major New York comedy clubs, playing opposite Norm McDonald in the 1998 big-screen comedy "Dirty Work," and landing a job with Stern.
Along the way, Lange began taking painkillers -- sometimes as many as 50 Vicodin a day -- until he graduated to heroin.
Lange's struggles with heroin continued even after he finished his 2008 memoir. At the end of the paperback edition released last April, he claimed to be clean for a few months.
"But hey, who knows how long that will last," he wrote. "I'm a rough case of addiction."
There's a long list of comedians who have struggled with drug addiction. Those who died young include Sam Kinison, John Belushi and Chris Farley.
"I can remember faking it," Cavett told ABCNews.com. "There I was on the monitor singing and laughing and thinking if they only knew how I feel I'd be amazed."
Cavett said with the help of a "modest amount of a couple of meds" he hasn't had a problem in a long time.
Then there are the difficult childhoods that helped hone the humor of other famous comedians.
Carrey opened up about having to get a job as a janitor at age 16 when his father lost his job and the family "hit the skids." He told "60 Minutes'" Steve Kroft in 2004 that his anger at the world during that time fueled his comic dreams.
"People need motivation to do anything. I don't think human beings learn anything without desperation," Carrey told Kroft. "Desperation is a necessary ingredient to learning anything, or creating anything. Period. If you ain't desperate at some point, you ain't interesting."
At 17, he was working comedy clubs in his native Canada and by 21 he had made his first appearance on "The Tonight Show."
Stephen Colbert lost his father and two brothers at the age of 10 when they died in a plane crash.
"I think I did my best to cheer my mom up," Colbert told Morley Safer on "60 Minutes."
The tragedy also sowed the seeds of the successful political satirist he would become as host of "The Stephen Colbert Show."
"I know that after they died, nothing -- I was 10, you know? I was still in school; it was in elementary school -- but nothing seemed that important to me," he told Safer. "I had immediately had sort of a, I won't say a cynical detachment from the world. But I would certainly say I was detached from what was normal behavior of children around me. It didn't make much sense. None of it seemed very important. And I think that, you know, feeds into a sense that acceptance, or blind acceptance of authority, is not easy for me."
Not every comedian appears to have a dark side. There are some notable exceptions.