“Why do they do it” Gore Vidal, playing a talk show host, asks psychologist Henry Carter (Kevin Spacey), therapist to Hollywood big-shots, as Jonas Pate’s “Shrink” slides into its last reel. Vidal, looking puffy and weathered, is inquiring about suicides, but he might as well be asking about people who choose to make movies as phony as this one. It’s impossible to believe a single character or line of dialogue in it.

Carter, you see, is one of those physicians who’s sicker than his patients, a man angst-ridden over his own wife’s decision to take her life who spends most of his time in a haze of marijuana smoke, courtesy of a chatty drug dealer named Jesus (Jesse Plemons). And what a bevy of troubled souls he’s supposedly treating. There’s Patrick (Dallas Roberts), one of those powerful agents who’s constantly barking out orders, especially to his sweet, pregnant assistant Daisy (Pell James), who is himself an omnia-phobe. And Jack (Robin Williams, whose name is omitted from the credits but unfortunately for him is still identifiable) as an alcoholic movie star itching to cheat on his wife. And Kate (Saffron Burrows), an actress just turned thirty (and thus no longer suitable for many roles) whose country-music husband is having affairs on the side. Not yet on his patient roster but careening toward a crash is Irish action star Shamus (Jack Huston), while Henry’s therapist dad (Robert Loggia) and his young friend Jeremy (Mark Webber), an aspiring writer toiling away as a valet parking attendant, try to help him. Into this unholy mix of cardboard characters is thrust Jemma (Keke Palmer), a self-destructive high-school kid who’s mother killed herself and now skips class to watch movies at an all-too-convenient revival theatre (you know, the sort that’s been driven out of business by DVDs but still gets crowds in this kind of fantasy film). Henry’s induced to treat her pro bono.

There’s a lot of interaction among these figures, but none of it has the slightest ring of authenticity, and the links among them tend to be contrived and implausible. That’s especially the case with the circumstance that brings a bunch of them together at the close—a coincidence so unlikely that it’s impossible to take seriously, but even worse leads to a happy ending even phonier than everything preceding it. (The close also undermines the dark, caustic attitude toward the business that’s pervaded the picture until then, suggesting that moviemaking can actually be redemptive! If this was supposed to be a tongue-in-cheek joke, it certainly does come off that way.)

In part what happens in “Shrink” is supposed to be an edgy commentary on Hollywood excess and the grim realities of celebrity in particular and the movie business in general, but mostly the jibes are pretty puerile stiff dumbed down to People magazine level so that anyone whose understanding of studio processes has been formed by regular viewing of Entertainment Tonight can feel superior by “getting” them. And in large measure the script by Thomas Moffett is apparently intended as a serious refection on grief and loneliness. The combination of such disparate elements might be incongruous if the material in either part were particularly good, but here both elements are equally bland and tedious: what passes for sharp satire here is as shallow and inconsequential as the big emotional moments that try to be wrenchingly revelatory. And at times it appears the picture’s aiming for both effects simultaneously, as in Spacey’s awful meltdown sequence with Vidal, in which the actor is at his very worst.

That’s not to say he’s not bad elsewhere, too; this is one of the dullest, least varied performances he’s ever given. No one else makes much of a positive impression either, but some are worse than others: Roberts’ turn as the super-aggressive agent is an SNL character sketch interminably dragged out, and Huston’s preening action star goes nowhere fast. One also has to feel sorry for Loggia, if for no other reason that he has to quote Soren Kierkegaard—the sort of thing that practically defines desperately pretentious screenwriting. Cinematographer Lukas Ettlin is responsible for the dank, unpleasant look of the movie, and editor Luis Carballar for its sluggishness, but it’s difficult to imagine that anybody could have done better with what Moffett’s trite script and Pate’s leaden direction had to offer.

Almost everyone’s miserable in “Shrink”—but nobody more so than a person unlucky enough to be watching it.