PRAGUE — 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.