Theatre: The Trick Is to Keep Breathing Royal Court, London

Not enough good parts for women? One way round the problem is the job-creating split-self approach to character. True, men have been in on that tactic: the hero of Brian Friel's Philadelphia Here I Come, for example, is a comic double-act that dramatises his internal division.

More recently, though, it's a preponderance of fractured females we've seen on the stage. Both Michel Tremblay in Albertine In Five Times and Edward Albee in Three Tall Women present their protagonists as a communing cross-section of the selves they were at different stages of their lives. In Sarah Daniels's Beside Herself, a seemingly "together" and efficient middle-class lady was stalked by a waif-like adult in a little girl's clothes who represented the sexually abused child, buried but far from dead, within her.

The Daniels is the nearest equivalent I can think of for the handling of the central character in Michael Boyd's stunning stage adaptation of The Trick Is to Keep Breathing, the Janice Galloway novel that takes you on a painful, often wildly funny journey into the mental breakdown suffered by Joy, a thirtysomething Scottish teacher after the accidental death by drowning of her married lover. Jennifer Black is the self as presented to the world and to the psychiatric profession, which directs its maddeningly unhelpful questions at her ("So why do you think you have been sent here?") from the elevated distance of the circle. Tracy Wiles, the youngest of the trinity, is the howling primal Joy, who scissors and paints red a self-mutilating "ME" into the drop-screen.

Still think you might give this one a miss? Well, don't, because, pumping a wonderfully scabrous energy into the piece and offering a bitterly hilarious commentary on the self-help books and inane therapies proffered, Siobhan Redmond's third Joy is like some rangy, reckless, mood-swinging alternative comedienne. Exorbitantly indiscreet, she paces around in agitation, and mimes strangling the health visitor whose idea of comfort is to say that she has seen it all before. This Joy swigs gin and holds the bottle up in a defiant toast to the screen when it flashes the advice printed on anti-depressant bottles "Do not operate machinery. Avoid alcohol."

The grimly droll counterpoint of such titles, the screech of microphone feedback, the ghosting of voices, the plink of a piano and the abstract setting combine to give the piece the nerve-jarring, disjointed feel of mental chaos. A surprising number of coffins seem to have accumulated round Joy's bed and, in one typical episode, her dead mother reappears to give these objects a house-proud dusting before having a well-earned rest and a cuppa in one of them. "Everything worth having is as hard as nails," she declares cheeringly.

In the second half, it becomes evident that Joy's family has a long history of mental illness. Does this make her a special case rather than the reporter of a hellish experience any of us might suffer. I think not: show me the family that can claim immunity in this regard. A remarkable, viscerally mind-broadening evening, then, and one bound, you'd have thought, to send people racing to Galloway's novels.

To Sat. The Barclays New Stages Festival continues to July. Booking: 0171-730 2554