Madness and Modernity, Wellcome Collection, London

In 1900, the Austro-Hungarian Empire was disintegrating and its doctors were discovering nervous diseases by the bushel. Small wonder that the artists of its cultured capital, home to the greatest psychiatrist of all, were inspired by decay.

Madness and Modernity, on the mutual influence of those who portrayed and treated the mentally ill of Vienna, has some fascinating material but also the usual flaw of such exhibitions. While the strictly scientific shows at the Wellcome are superb, the artistic ones lack focus, like its magpie founder, Henry Wellcome, who amassed more than a million objects, ranging from treasures to curiosities.

What do the Persian rug draping Sigmund Freud's couch, or his little bronze gods, tell us about his effect on the visual arts? Why devote a room to the watercolours of a patient? And the fabulous model, with golden angels and golden dome, of a church designed for the residents of an asylum could be any grand Jugendstil building.

Purkersdorf sanitarium is another story. This intimidatingly elegant building not only was designed by Josef Hoffmann, a founder of the Wiener Werkstatte; it had chairs, sconces, even ashtrays created by him, artifacts copied by fashionable Vienna. The ambiance was intended to be hygienic and free from disturbing associations, but one wonders if the patients saw it that way.

The centrepiece is the work of Egon Schiele, echoing that of Jean-Martin Charcot, a neurologist who photographed his disturbed, misshapen patients nude. Schiele's self-portraits show a body emaciated and twisted like theirs. Some suggest the frenzy of madmen who feel imprisoned by clothes; in others the intensity is erotic, as in one of the artist masturbating.

But the strongest presence is unseen, suggested only by the label of a Kokoschka portrait. Contemporary critics held their noses at its "foul smell". A generation on, Kokoschka would be hung in the notorious Degenerate Art exhibition, in which Cubists, Expressionists and Jews were ridiculed as diseased by a society gone mad.

To 28 June (020-7611 2222; www.wellcomecollection.org)