The race is on to revamp the romcom. The Ugly Truth sought to enhance the formula by toying briefly with reality. Now, Love Happens attempts to soup up the recipe by chucking in dollops of death, grief and guilt. ­The critics don't like this film any more than its predecessor. Nonetheless, the romantic comedy refurbishment campaign seems unlikely to falter. After all, a touch of sex stereotype reassignment was enough to equip The Proposal to sweep all before it. If the nips and tucks are skilful enough, this hoary genre can, it seems, still do the business. What, however, is the business that it's doing?

Romcoms don't merely provide an evening's harmless escapism. They help underpin one of the most potent doctrines of our culture: the sanctity of romantic love. It's a doctrine in which many find relief from the materialism, apathy and banality of a society no longer hallowed by religious transcendence. Yet it comes at a price.

The involuntary cognitive state that Jennifer Aniston finds herself depicting so frequently is real enough, but not particularly mystical. Brain scans show it to be generated by the frisky interaction of chemicals like norepinephrine and dopamine. If this hubbub's triggered by recognition of genetic quality, as now seems to be assumed, that would explain why Aniston and her ilk have to be so annoyingly good-looking.

For some people, including doubtless many romcom addicts, the pursuit of what's now called "limerence" by some researchers becomes an overriding goal. Failure to encounter this experience can blight the lives of those who've come to believe that nothing else really counts. Yet even those who succeed in falling in love are unlikely to find that this solves all their problems.

Apparently, once the romance chemicals have done their little dance for a bit, the hypothalamus spoils the party by releasing a hormone called oxytocin, which puts something of a damper on things. "True love" doesn't last. Studies conducted by psychologist Dorothy Tennov found that three years' blissful limerence is pretty much the best we can hope for. Your mum would have told you as much. Nonetheless, Aniston's characters' real-life counterparts remain convinced that for some reason they're exceptions to this rule.

The discovery that this isn't so provokes intense bitterness. If romantic love is all that matters, its loss must be a catastrophe. Its expropriation must be avenged and its pursuit commenced afresh. Hence the ravages of divorce, potentially turning former intimates into ruthless foes, possibly inflicting cruel heartache on their children. Romance, it turns out, destroys less glamorous but ultimately more important bonds of affection.

What we call love induces some of the worst behaviour that we're likely to encounter. Yet when this occurs, it usually invites no censure, let alone punishment. Romantic love is a get-out-of-jail-free card that legitimises actions which would otherwise be thought contemptible. Home-wreckers steal something cherished far more deeply than money or possessions. Nonetheless, they go on to build their happiness on the misery of others without having to endure the slightest disapproval. After all, they had no choice but to do what they did: they were in love.

Jennifer Aniston is herself a victim of this process, perhaps currently the world's most celebrated. Yet she continues to devote her career to fuelling the furnace that's consumed her own romantic hopes.

In other cultures, romantic love enjoys no comparable status. Our own ancestors might find our veneration of it as puzzling as we find their worship of pagan gods. In our otherwise disrespectful age, the persistence of its dominion is rather remarkable. Would it have proved so enduring without the big screen's relentless promotion of its supposedly limitless benefits?

On the small screen, romantic passion gets cut down to size. Come over a bit too torrid in The Vic and you'll just raise sceptical eyebrows. The movies, on the other hand, are enthralled by its glitter and grandeur. They feed off it greedily, and in so doing, feed it. More's the pity.