Sarah Sands: Three cheers for the happy-mongers

The film director Mike Leigh is heralded as both a novelty and an inpatient for his new film Happy-Go-Lucky. His interviewer on Friday's Today programme, Sarah Montague, chided him gently. What was his Damascene conversion from the miserable and the absurd? Why move from the savage reality of Thatcher's Britain to this Teletubby world of well-intentioned primary teachers?

Leigh tried to protest that he has always worked within shades, but then he dropped his defensiveness. The truth is that he is happy! And he has dared reflect humanity's resourceful capacity for happiness within his film. It will not endear him to critics. See how Alexander McCall Smith, another happy man, has offended his miserablist-chic critics.

There was a film called Happiness, which came out 10 years ago. It was naturally an ironic title. Happiness is a mask. In this case, the good husband in the film was secretly molesting the classmates of his 11-year-old son. Culturally, happiness has come to represent a sinister government lie. When Tony Blair's strategy unit held a "life satisfaction" seminar in 2002 it was written off as political lunacy. When David Cameron raised happiness, he was shouted down as a toff. His point that money does not insulate you from unhappiness, that Britain is both wealthier than in the 1950s and less contented, was regarded as bad taste. If the economy is tanking and we are running out of food and terrorism is on the rise and we are destroying planet itself, then this is hardly the time to talk of happiness.

Leigh and his fellow happy-mongers would argue that this is exactly the time to consider happiness. It is a glorious paradox that private happiness can flourish during the collapse of the state or even the world. The most cheerful person I have met recently was the scientist James Lovelock, who believes the human race has about 40 years left before most of it is wiped out by global warming. He said he felt the same acute sense of pleasure that he experienced during the Second World War. Human relationships are heightened by a backdrop of catastrophe.

Leigh is risking ridicule and incomprehension by coming out for happiness. The publishing industry has been kept afloat of an ocean of tears over the past decade. Misery memoirs have made commercial fortunes. A favourite question asked on book programmes is whether the money and fame made the suffering worthwhile. The writers admit a strange gratitude towards their misfortune. Even J K Rowling is superstitious about letting go of her young, poor self, scribbling away in the café, although her life is transformed.

I noticed the extraordinary prejudice against happiness when I took the job as editor of British Reader's Digest. My pals in newspapers were wildly suspicious of the founding ethic of the Reader's Digest Association, which is optimism and goodwill. They equated optimism with escapism and goodwill with banality.

Leigh's point is that optimism is not denial but acceptance. It is certainly not banal. It is much harder to be positive than negative. It demands tremendous resilience. I have witnessed severe depression at close quarters and its characteristics are extreme anxiety, sometimes paranoia, an inability to feel empathy or engagement with the world, a desire to withdraw, a heavy sense of dread.

Prosperity, success, or more democratic happiness – triggered by sunshine, children, flowers, music – cannot help the clinically depressed. Happiness is not a social status but a state of mind. It is why so many who work in mental health favour cognitive behavioural therapy to drugs. The way to heave depressive patients out of the abyss is to retrain their minds. Each negative thought must be wrestled into a positive one. Where there is suspicion, create trust, where there is revulsion, bring generosity, where there is emptiness, infuse love.

If happiness has to be taught, letter by letter, then should we not start early? Some medical surveys claim one in five children suffers from emotional disorders. Suicide is the third highest cause of death between the ages of 15 and 24. The main character in Happy-Go-Lucky is a primary teacher who she saves a disruptive and unhappy child. The trouble with addressing happiness in children is that you hit uncomfortable truths. The children carry the sins – or the genes – of their parents. Children from broken homes are unhappier. Children of depressed parents are vulnerable. Happiness is not a cop-out, it is social and parental duty. And the bloodier the circumstances, the braver the smile.

The reason we shy away from the happiness imperative is that it demands a degree of self-renunciation. If you are married, maintain friendships and do some form of voluntary work then you are statistically more likely to be happy than a workaholic singleton who looks to spas for spiritual renewal. You just are. We know what makes us happy but it is not particularly compatible with contemporary living. The philosopher Seneca boiled it down to one word: virtue. The less cluttered and the more outward-looking you are, the happier you will be.

One of the empirically tested obstacles to happiness is comparison. Once you know what your colleagues or neighbours are earning, you will never sleep easy. This applies also to countries. When the rich/poor gap becomes too gaping, there is a kind of national depression. It is what happened under Blair and it is evident in the superpowers of Russia and China. The philosopher Jeremy Bentham addressed this in his " happiness principle". He spoke of the "greatest happiness of the greatest number". But the happiness Leigh talks of has nothing to do with the levers of state. It a private optimism based on a trust in the good of mankind.

The last time the BBC website ran a happiness index, the online responses of what created happiness were all of a pattern: children and grandchildren, stopping to look at a bird's nest, buds on the trees, the smell of new grass, gardens, gardens, gardens. We may look for job satisfaction in business, or politics, or the City, but nobody describes it as a philosophical route to enlightenment.

When I spoke to Rachel de Thame about her chosen career as a gardener she gave a trance-like account of the seasons, creation and fruition, and perfect harmony. We know the route to happiness. The more interesting question is whether we want to take it. Some of the early philosophers saw life as strewn with stones and hardship as a duty. Heraclitus celebrated strife and opposition. Diogenes called for the austerity of self-sufficiency. Aloneness is a purer state than community. All bonds are illusory. I do not believe that a bleak view of the purpose of existence is incompatible with happiness.

Even Leigh acknowledges that some people have luckier lives than others. Genetic illness has a cruel preference. I remember Nigella Lawson's weariness on the subject of global warming: was this planet so fabulous that it was worth saving? Her dark sense of fate, certainly influenced by the death from cancer of her mother, sister and husband, does not prevent her customary gaiety, however. Nigella is an example of happy-go-lucky in the Leigh sense. She cares for and loves others, whatever her own unruly thoughts. She does not make a brand of unhappiness. Society tried to make her a favourite victim and she fought against it, eating, loving, marrying, laughing. Her philosophy that the answer to tragedy is to stuff a chicken is so merry and brave.

Leigh also seizes the day. "I come from a long line of early deaths from heart attacks so I'm extremely lucky to be here at all," he said. Ask for no more. Be happy.