(CNN) The most important hour of "The History of Comedy" -- an eight-part CNN documentary devoted to stand-up -- might be the most serious and sobering: the high toll comedy exacts on its practitioners, from depression to substance abuse.
The tears of a clown almost sounds like a cliché, but given the high-profile examples of comics who died young or took their own lives -- among them John Belushi, Chris Farley, Robin Williams and Richard Jeni -- it's more than just a song title. And in that upcoming segment of the program, subtitled "Spark of Madness," comics talk with considerable openness and honesty about the exaggerated highs and lows associated with their work.
"A lot of comedians are people that are very introverted, very shy, very sensitive to humiliation," says Patton Oswalt, adding that it's common for them to be "a little narcissistic, a little damaged."
As Gilbert Gottfried notes, it's not unusual for people to lament after a tragedy, like Williams' suicide in 2014, how someone could be so buoyant and talented and yet so plagued by demons and excesses. The two, he suggests, are intertwined, much like the masks of comedy and tragedy.
What "History of Comedy" does within that hour is to bring what are often viewed as isolated incidents into context. Programmed to probe for universal truths and bare their souls on stage, the comics interviewed also prove extremely open and honest in discussing these issues, including how drugs often serve as a means of replicating the high that they get from performing.
This phenomenon is hardly news within the comedy community. Indeed, there's audio of Williams hero and inspiration, Jonathan Winters, discussing his own nervous breakdown at the height of his career. In 2011, Jamie Masada, owner of the comedy club the Laugh Factory, retained a psychologist to serve as a resource to comics who might be having issues, motivated by Jeni's suicide and Greg Giraldo's fatal overdose.
The documentary also arrives at a moment when two scripted series will explore the lives of comics, starting with "Crashing," starring Pete Holmes, which premieres on HBO later this month. Showtime will follow that this spring with "I'm Dying Up Here," which chronicles the L.A. comedy scene in the formative 1970s.
"History of Comedy" examines several aspects of the craft, kicking off with an installment subtitled "F***ing Funny," tracing the evolution of profanity on stage, from burlesque to Lenny Bruce and George Carlin. Other chapters look at women in comedy and comedy's relationship to politics.
"Spark of Madness" isn't the funniest or most entertaining, of the episodes previewed. Yet for anyone interested in comedy -- and who has perhaps wondered how someone who brings audiences such joy can be so personally troubled -- it's almost surely the most important.
"The History of Comedy" premieres February 9 at 10 p.m. on CNN.