The high cost of feeling low

Depression is, according to a World Health Organization study, the world's fourth worst health problem, measured by how many years of good health it causes to be lost. By 2020, it is likely to rank second, behind heart disease. Yet not nearly enough is being done to treat or prevent it.

The study, led by Saba Moussavi and published last month in The Lancet , also revealed that depression has more impact on the physical health of those who suffer from it than major chronic diseases like angina, diabetes, arthritis, and asthma. Yet in the same issue of The Lancet , Gavin Andrews and Nickolai Titov, researchers at the University of New South Wales, reported that Australians with depression are far less likely to receive an acceptable level of care than patients with arthritis or asthma. This pattern is consistent with reports from other developed nations.

Treating depression is often, if not always, effective, and without it, those who suffer from depression cannot live happy, fulfilling lives. But, even in narrow cost-benefit terms, it makes sense to spend more on treating depression.

A study of 28 European countries found that depression cost them €118 billion in 2004, or 1% of their combined GDP. The cost of treating depression accounted for only 9% of this huge sum. A much larger share was lost productivity. Richard Layard, of the Centre for Economic Performance at the London School of Economics, has said that mental illness is Britain's biggest social problem, costing 1.5% of GDP. He estimates that while treatment may cost £750 per patient over two years, the result is likely to be an extra month of work, worth £1880. Lord Layard advocates more psychotherapy rather than drug treatment.

In the United States, a research team headed by Philip Wang of the National Institute of Mental Health in Rockville, Maryland, reported similar results last month in the Journal of the American Medical Association . Wang's team conducted a randomized controlled trial that showed that depression screening - to find workers who could benefit from treatment - was cost-effective, reducing health insurance costs to employers, decreasing absence due to sickness, and increasing job retention and productivity.

Depression is also costly in developing countries. In China, according to a recent article by Teh-wei Hu and colleagues in Social Psychiatry and Psychiatric Epidemiology , depression costs 51 billion renminbi, or more than $6 billion, per year at 2002 prices. A few years ago, a research team led by Vikram Patel reported in the British Medical Journal that depression is common in Zimbabwe, where it was often known by a Shona word that means "thinking too much."

Around the world, many primary care physicians underestimate the seriousness of depression. Many of them lack adequate training in recognizing mental illness, and may not be up to date with treatments options. Patients, too, may fail to seek treatment, because mental illness still carries a stigma that can make it harder to acknowledge than a physical illness.

The problem has been aggravated, in the US at least, by the refusal of some health insurance policies to cover treatment for mental illness. Thus, the US Senate's recent approval of the "Mental Health Parity Act" is a significant step forward. The legislation, which still has to pass through the House of Representatives, would require health insurance plans provided by employers to cover treatment for mental illness at a level similar to coverage for general health care. (Unfortunately, the legislation will do nothing for the 47 million Americans who have no health insurance at all.)

Depression is an individual tragedy that is multiplied more than 100 million times worldwide. So, while we can and should do much better at treating it, perhaps the more significant question is whether we can learn to prevent it.

Some depression appears to be genetic, in which case genetic therapy may ultimately offer a solution. But much mental illness appears to depend on environmental factors. Perhaps we need to focus on aspects of living that have a positive effect on mental health. Many recent studies show that spending time relaxing with family and friends contributes to how happy people are with their lives, while long working hours, and especially long commuting times, contribute to stress and unhappiness. Of course, relaxed and happy people can still become depressed, and stressed and unhappy people may not be depressed, but it is a reasonable hypothesis that happier people are less likely to become depressed.

LaSalle Leffall, who chaired the President's Cancer Panel, wrote to President George W. Bush in August, saying, "We can and must empower individuals to make healthy choices through appropriate policy and legislation." If that is true for encouraging healthy diets and discouraging smoking, it is no less true for lifestyle choices that promote greater mental health. Governments can't legislate happiness or ban depression, but public policy can play a role in ensuring that people have time to relax with friends, and pleasant places to do it.

(Peter Singer is Professor of Bioethics at Princeton University. His books include Practical Ethics, Pushing Time Away, The Moral of the Story, and, most recently, The Ethics of What We Eat.)