Keir Gilchrist, left, and Zach Galifianakis star in It's Kind of a Funny Story. (Focus Features)

The subject of mental illness has given us some indelible movie moments. There’s a vicarious thrill that comes from seeing characters lose control, and it can set the stage for all sorts of cinematic fireworks — witness the outsized, go-for-broke performances delivered by Angelina Jolie in Girl, Interrupted (1999) or Jack Nicholson in One Flew Over the Cuckoo’s Nest (1975).

The filmmakers ditched any serious commentary on depression in favour of a limp Juno-style comedy.

But where those charismatic characters acted out, depression often takes place within, and it’s a tough task to turn an illness characterized by loss of appetite, lethargy and despairing thoughts into an engaging movie. Play it straight and you risk putting an audience to sleep; go for laughs and you could trivialize the issue. Aim for a mixture of both and the result is the unsatisfying screen adaptation of Ned Vizzini’s young-adult novel It’s Kind of a Funny Story.

Things begin on an admirably edgy note, with 16-year-old Craig Gilpin (Keir Gilchrist) perched high atop the Brooklyn Bridge, contemplating ending it all. Though this freefall opener proves to be a dream sequence, the suicidal impulses are still there when Craig wakes up. Dogged by bouts of stress-induced vomiting, overwhelming fears about his academic future and an unrequited crush on his best friend’s girl (Zoe Kravitz), Craig decides he needs help, and checks himself into an adult psychiatric ward for a five-day stay.

Indie directors Anna Boden and Ryan Fleck initially adopt the unsentimental approach that made their remarkable previous films, Half Nelson (2006) and Sugar (2009), feel more like documentaries than fictional dramas. Craig’s problems could be chalked up to a case of privileged-teen angst, but to him they feel insurmountable, and the filmmakers take their troubled character seriously.

The boy’s initial moments at Argenon Hospital are unsettlingly realistic – Craig’s worried expressions and flat, affectless voice are recorded plainly, under the soul-sucking glare of waiting room lights. Yet no sooner has Craig checked into the Three North ward than It’s Kind of a Funny Story takes a turn for the upbeat. The patients in this asylum are all colourful, and drawn in broad strokes that reduce them to quirky types. There is Craig’s skittish Egyptian roommate, Muqtada (Bernard White); a woman known as the Professor (Novella Nelson) who’s paranoid about the U.S.A. Patriot Act; and a Hasidic acidhead known as Solomon (Daniel London). A doe-eyed self-mutilator named Noelle (Emma Roberts) makes a more lasting impression, as does Bobby (Zach Galifianakis), a lifelong depressive who takes it upon himself to act as Craig’s friend and mentor.

The budding friendship between Bobby and Craig provides some of It’s Kind of a Funny Story’s finest, most authentic moments. Gilchrist and comic Galifianakis have a nice, easy banter, particularly in a scene where they sneak off to shoot some hoops. Galifianakis acquits himself well in his first meaty dramatic role – he brings a much-needed element of surprise and danger to the movie in one crackup scene, and also adds just the right hint of sadness when he muses that he’d trade everything in his messy life to get a chance to be Craig for one day.

But from that point on, It’s Kind of a Funny Story is a mess. The movie suffers from bipolar disorder – cycling rapidly between dramatic scenes in which Craig’s therapist, Dr. Minerva (Viola Davis, stranded in a lame role), helps him articulate his inner anxieties, and more crowd-pleasing moments when Craig and Noelle flirt and race through the hallways in hospital scrubs.

Stylistically, things are every bit as disjointed, with Boden and Fleck piling on voice-over narration, freeze frames, childhood flashbacks and bits of twee animation in an effort to keep things lively. By the time the glam-rock-attired patients belt out a spirited rendition of Queen’s Under Pressure, it becomes painfully clear that the filmmakers have ditched any serious commentary on depression in favour of a limp Juno-style comedy.

To be fair, many of It’s Kind of a Funny Story’s flaws are also in Vizzini’s source material, which relied on cartoonish secondary characters and some of the glib, shrugging narration that mars It’s Kind of a Funny Story’s latter stages. That still doesn’t excuse Boden and Fleck’s poor decisions throughout – like hinting that Noelle’s character is an abuse victim in one scene, and portraying her as a spunky, indie-band-worshipping teen the next. Similarly, having Craig utter disclaimers like “this gets pretty sappy” right before some of the movie’s most hokey scenes feels like a serious cop-out.

The film should still play well with a teenage audience, since Craig’s problems are ultimately attributed to his clueless parents, high-pressure prep school and the inner artistic gifts he’s never been able to express. He’s a Boy, Interrupted — a sensitive, well-meaning Holden Caulfield type who would likely thrive with the help of a few make-out sessions and a refill prescription for antidepressants.

Though this is mildly entertaining, it’s also far too easy, and It’s Kind of a Funny Story’s phoniness winds up being thoroughly depressing. There might still be hope for Craig. Everybody else, however, is reaching for the Zoloft.

It’s Kind of a Funny Story opens Oct. 8.

Lee Ferguson writes about the arts for CBC News.