The Sketch: Freudian-slip funsters find asylum in chamber of errors

"MENTAL ILLNESS is as common as asthma," announced Frank Dobson yesterday. "It affects as many as one in six adults at any one time."

There were about a hundred MPs in the chamber when he said this, which suggested 16 or 17 of his colleagues might be showing signs of mild delusion if the assembly were genuinely representative of the nation at large. But they are not - if anything, the ratio in Parliament is likely to be rather higher than in the general population, given the established connection between high achievement and mental fragility.

The absent villain here was Care in the Community, which Mr Dobson had come to pitch into a pauper's grave, but Honourable Members have long been exempt from such programmes. Outside of an election year, they know they won't find themselves turned out on to the streets, where they might trouble the public by shouting aggressive questions about fiscal autonomy for the Scottish parliament. They already have their asylum, a Victorian Gothic pile in which they can pursue their obsessions protected by a diligent and caring staff; Betty Boothroyd may be strict but she is no Nurse Ratchett and only waves the strait-jackets when other therapeutic interventions have failed.

But if Mr Dobson's figures are correct, they can't all be mad - which puts a particular premium on identifying the tiniest symptoms of derangement. This isn't easy, given the general peculiarity of behaviour in the House. What psychiatrists call "dissociation of effect", for instance, is commonplace in the Chamber. This is when a patient bursts out laughing or roaring with anger, despite the absence of any obvious stimulus. Yesterday, during Ann Widdecombe's reply, Paul Boateng, who usually appears broadly sane, suddenly went "Har, har, har!" employing the mirthless, italicised laugh members use to convey contempt. On the Tory benches, John Bercow was twitching and jerking like a bad case of shell shock, while I noticed also that Dr Liam Fox, up against Donald Dewar in Scottish questions, had written his notes in green ink, often accepted as an unambiguous indicator of mental disturbance.

But for all these symptoms there were also innocent explanations. Psychoanalytic approaches are no more successful either, given that politicians are subject to inhibitions over and above those felt by the rest of us. Freudian slips, for instance, are unlikely to open a window on the inner psyche of a politician, only into the cavity wall between public presentation and private opinion. Mr Dobson, a decent and diligent minister, is rather prone to these involuntary revelations - a couple of weeks ago, discussing pay rates in the NHS, he told the House "we all know that pay increases have to be avoidable ... er ... affordable".

Yesterday he thanked Nicholas Winterton for welcoming his statement, saying he had been "more supportive than the present government um - than the previous one". Ann Widdecombe had earlier sought a guarantee that there would be "no enforced medication of parents - I mean patients". This seemed more promising as a diagnostic clue, after references to "inappropriate discharges" and a particular interest in closing mixed wards in mental hospitals. Does she secretly dream of dosing the water with bromide and putting an end to all inappropriate discharges, inside the NHS and out? Well, probably not - if she suffers from neurosis it is likely to be only that occupational disease of adversary politics, a phobia of admitting the other side have done something sensible. Still, it is very confusing. One can only sympathise with the journalist overheard approaching a member of Mr Dobson's team and asking for help - "This mental health statement," he said wistfully, "any chance of an idiot's guide?"