Artists find nothing quite as fascinating as themselves. When the Medici started their celebrated collection of artist self-portraits, housed in the corridor that Giorgio Vasari built in 1565 to link the Uffizi via the Ponte Vecchio with the Pitti Palace, they set in train a cult of the self that pervades contemporary art today.

Walk through any graduate art show and you’ll see the signs: the shaky video work, the obscure narratives, the fetishistic self-absorption, the over- written “artist’s statement”. The blame for much of this selfimportance can be laid at the door of Romanticism, that seizure of the imagination that dominated the 19th century, a period when artists shook off their feudal ties with the established order and started polishing the first-person pronoun.

What emerges from Rebels and Martyrs, a new exhibition at the National Gallery in London, are the stories of how artists constructed their image as outsiders, adopting the pose of bohemian geniuses as a means of heightening the regard in which they were held. Of these, the French realist painter Gustave Courbet was perhaps the most brazen: his painting The Meeting (Bonjour Monsieur Courbet) of 1854 shows the artist sporting a dramatically dark and long beard, out on a country walk and being greeted by one of his patrons, who is accompanied by his manservant.

The composition reworks the New Testament account of Christ’s encounter with two Disciples on his way to Emmaus, something that Courbet’s contemporaries would have immediately recognised: the implied equation of Courbet with Christ, the ultimate martyr, would not have gone unremarked. In the end, Courbet, exiled from France after his involvement in the Paris Commune of 1871, died in poverty a broken man.

And what spurred on the Romantics’ self-absorption? As one of the exhibition’s curators, Michael Wilson, writes in the accompanying catalogue, “the religious scepticism of the 18th century had left a spiritual void which was now filled by a belief that the mystery of existence could not be comprehended through reason but only grasped by each individual emotionally through the imagination and intuition”.

The reasons why artists felt disillusioned with the established order, in which they — depending on their talent and circumstances — might occupy a position fluctuating between lowly artisan and individual genius, are complex and various. Nationality was one factor: artists such as Théodore Géricault and Eugène Delacroix living in France after the defeat of Napoleon in 1815 had a very different perspective to artists such as Samuel Palmer, Henry Fuseli and William Blake working in England.

Proximity to cities such as London, Paris and Rome and the consistency of patronage were other important factors. But what united many artists working then was the growing recognition that the intensity of creative vision and the struggle to express it was itself a fitting theme that should permeate their work.

It’s a theme that has bewitched Hollywood, with po- faced productions such as Lust for Life (1956), with Kirk Douglas apeing Van Gogh, The Agony and the Ecstasy (1965), giving us Charlton Heston wrestling with the statue of Michel- angelo, and Basquiat (1996), Julian Schnabel’s biopic of the eponymous artist, and more.

The BBC’s drama series The Impressionists is a more recent example of how heavily the burden of creative expression is seen to weigh on artists’ shoulders. In this, artists are alone more often than not: from Caspar David Friedrich’s isolated figures set high on a hilltop against the cloud line, as in The Wanderer Above the Mists, or musing at the edge of the northern seas, to the numerous images of artists’ cold and shabby studios, isolation is given as the context in which this burden is most keenly felt.

Back in the 19th century, isolation, and its frequent corollaries, poverty and physical and mental illness, could be genuinely dangerous and a cause of real suffering. Many were, literally, “martyrs to their art”, rebelling against the social and ethical mores of their time. The personal costs could be huge: while Edvard Munch’s The Scream has become an overused icon of adolescent angst, his Self Portrait in Hell (1903), showing the Norwegian artist standing naked against a backdrop of flames, is a far more telling image of despair.

We should, then, be wary of protestations of creative angst, of rebellious posturing and exaggeratedly tortured personas, especially when it comes to artists. “A volcanic crater artistically concealed behind bouquets of flowers” is how Baudelaire once described Delacroix. But at least there was a volcano. Today, the options for artists when it comes to their social persona seem to veer between the reclusive Lucian Freud and the embedded (as it were) Tracey Emin, whose mouthy posturing has, with her active connivance, become just a commodity. In the West, at least, this ersatz form of rebelliousness has morphed into celebrity. Elsewhere, in countries with very different rules about freedom of expression, it can make you a real martyr.

Rebels and Martyrs: The Image of the Artist in the Nineteenth Century, National Gallery, London WC2 (www.nationalgallery.org.uk 020-7747 2885), June 18-August 28