First Night: Polar Bears, Donmar Warehouse, London

Prize-winning author Mark Haddon's first stage play is about the difficulty of living with someone who has bipolar disorder. Does it work? <i>The Independent's</i> theatre critic Paul Taylor, himself a sufferer, is in two minds

Mark Haddon made his name with The Curious Incident of the Dog in the Night, a deservedly lauded and prize-winning novel about the break-up of a marriage as seen through the eyes of a teenager with Asperger's syndrome. When I heard that he had written Polar Bears, a play about the stresses and strains of loving a female bipolarity sufferer, I'm afraid to say that my first cynical reaction was to wonder whether he started to collect disorders for creative exploitation across the art forms. What he would he be treating us to next? The first Alzheimer's musical? Tourette's syndrome explored as an ice spectacular?

My misgivings were exacerbated by the fact that I myself am bipolar. My case is not nearly as severe as that of Kay, the protagonist of his play, which is now unveiled in Jamie Lloyd's vigorous, sometimes serio-joky, sometimes bruised and poetic production at the Donmar Warehouse. But it has taken an intermittently costly toll on my family and me.

To commission a bipolar critic to review a play about the consequences of bipolarity might be thought by some to be roughly akin to hiring a horse to predict the first three past the post in the Grand National or (a joke that Beckett- loving bipolar sufferers will appreciate) to order the boot that's on the other foot to judge an arse-kicking contest. But while allowing that it's perfectly possible to be both an authority on the subject and a sufferer, as witness Kay Redfield Jamison, the author of the classic Touched by Fire, it's important that those with insider knowledge, so to speak, don't imagine that they have a monopoly of wisdom on the topic or that those who come at it from the outside are guilty of tourism.

As Haddon's play demonstrates, a "civilian" may be more sensitive than the sufferer to the damage that can be done to the nearest and dearest of the person who is having the extreme mood swings. In his debut stage drama, he proves that he can create comic dialogue that sometimes has an Alan Bennett ring; he can shape scenes so that they spring surprises; he can tell a story out-of-chronological-sequence so that by the back-and-forth jumps and juxtaposition, episodes sometimes contradict each other or shift from the objective to the subjective. This last talent is useful for a play that, like the heroine, is in two minds about what actually happens as events in the outside world and happenings in her head possibly conflict.

The play starts with a confrontation between John, Kay's kindly, sorely tried philosopher husband (Richard Coyle) and her brother Sandy (Paul Hilton), a manufacturer of supermarket check-out equipment who has always impatiently believed that she should just grow up. In a weird mood himself, John claims that the youthful Kay (Jodhi May) is dead but ironically not by her own hand. He says that he killed her accidentally during a fight. This idea is immediately, if perhaps provisionally, contradicted by a scene where we see Kay making a phone call from Oslo where she had been scheduled to go.

Polar Bears is at its best when it dramatises the terrible burden borne by people who love and care for bipolar sufferers. Attracted by what is magnetic and life-giving in their partners when they are on an upswing, they can feel dreadfully betrayed when their loved ones turn manic or secretly stop taking the medication. The problem, though, is that Haddon's play deals in faintly lurid extremities when the real dramatic interest in the condition lies, to my mind, in the greyer areas.

For example, like a lot of bipolar people, Kay – played by Ms May with a keen feel for her excitability and hectic allure – is given, when on a high, to bombastic delusions about her talents, in this case for art. She leads her husband to half-believe that she is on the shortlist for the Carnegie Medal for a children's book she has written and illustrated. But in a melodramatically staged scene, with pages cascading through a symbolically wrecked ceiling, her mother (Celia Imrie) disillusions John with the terrible truth. Kay has no talent whatsoever. Her illustrations are just childish scrawls. More telling, though, is the case of those bipolar sufferers who actually can express themselves artistically when on a high but can't follow it through and get dreadfully demoralised and disbelieving of their mood-dependent gifts when in troughs of depression. That situation throws up the kind of moral dilemmas (over whether to go on a holiday from medication so as to "bank", so to speak, some work while the going is good) that never confront Kay who has rapturous visions but no way of converting them into art and no children.

Peter Brook once said of Beckett that the depth of shadow in his work implied an intense light source but Kay's ups and downs don't seem mutually defining in this way (acute depression can feel strangely like the sublimity-in-reverse of intense joy). Instead, the highs are presented as a kind of possession, a take-over of the real Kay (whatever that is) by an irresponsible child.

The mother declares that, if they are truthful, all carers of the manic-depressive at one time or another have wished their charges dead. I would say that this is a libel on many such people who find themselves impaled, without rancour, on the intolerable paradox of needing to be a combination of parole-officer and drug pusher to a loved one whose loveable qualities are unfortunately inescapably part-and-parcel of what makes them, for periods, impossible to live with. Abandoned by Kay's father in the worst of ways (suicide by hanging) the mother is shown to be possessive of her daughter and possibly parasitic on her condition.

One of the best scenes is also one of the quietest. Kay goes AWOL and evidently has had a weekend of sexual reunion with an old college boyfriend (David Leon, who also plays her Geordie projection of Jesus). The husband and this revenant meet by the bed where she lies unconscious and instead of bitterness there is a kind of subdued fellow-feeling in their shared affectionate, troubled fascination for this volatile kite of a woman who is always liable to tug itself from their anxious grasp.