A milestone was reached toward the end of last year, and the press made no note of it. In October, the World Health Organization declared that now, among all the illnesses and forms of injury it measures, "
depression is the leading cause of years lost due to disability."
I have a personal stake in this announcement. In doubting reviews, I was twitted for claiming in my 2005 book, Against Depression, that "depression is the major scourge of humankind." This criticism was based on a misreading. What I had written was that the WHO and other organizations interested in public health were making that assertion. The full paragraph goes: "Groups around the world have undertaken the same effort using different assumptions and weightings. The results of these analyses are similar. Varied assumptions lead to a single conclusion: Not AIDS, not breast cancer, but depression is the major scourge of humankind."
I went on to explain how the WHO assesses disability. It uses a measure, called "disability-adjusted life years," or DALYs, that gauges how far a disease or injury robs a person of good health. If you live in a country where the life expectancy is 80 but cancer kills you at age 60, you have lost 20 good years; but likewise, if a birth injury partially paralyzes you and leaves you 25% disabled, then if you live to 80 you will also be judged to have lost 20 good years. Actually, the birth injury would be rated worse, because the measure values years in young adulthood slightly more than years in old age. Because major depression is so common and so severe in its effects, and because its onset is often early in life, it tends to stand out in surveys focused on DALYs.
I should add that the panels that devised the rating systems used by the WHO included few or no psychiatrists. Surgeons, pediatricians, and internists made the assessments. When the results of the first surveys emerged, the prominent place of depression surprised everyone. But the findings have been consistent over time. What has changed is largely the WHO's willingness to stand behind them and emphasize, as it did in its recent the press releases, depression's awful status. Still, here it is: the claim I was criticized for (but did not quite make) is now the official position of the preeminent authority on global health and illness.
The survey available when I was writing was based on 1990 data; the new report has updates from as recently as 2004. As had been predicted, depression has moved up in the standings - that is, it appears yet more disabling, compared to other conditions.
In truth, the status of depression has changed only modestly. Because they kill children at birth and so rob them of a whole life span, "lower respiratory infections" and "diarrhoeal diseases" remain at the top of the DALYs list. But those categories represent clusters of differing illnesses. Depression comes next, and it is arguably a narrower category.
If you set aside low-income countries and look either at middle- or high-income countries, depression is now absolutely atop the list, above ischemic heart disease and cerebrovascular disease, above traffic accidents, dementia, and diabetes. If you look regionally, here in the Americas, depression is also outright the most disabling condition, above violence and heart disease. For women, depression is the leading cause of disability everywhere, even in low- and middle-income countries, outpacing HIV/AIDS.
One can debate the WHO measures. They count each episode of depression as highly disabling; but then, they omit more minor episodes altogether. Also, they ignore links between conditions. For example, maternal depression is a potent risk factor for infantile diarrhea. Self-inflicted injuries, which are very common in poor countries, are counted as separate from depression. And really, wouldn't depression be a serious enough problem if it were judged only as disabling as cancer, heart disease, diabetes, or AIDS? Still, the WHO Global Burden of Disease study is the gold standard, and it finds depression to be, yes, the severest scourge.
Regarding science journalism, we live in strange times. When isolated academics use esoteric studies and idiosyncratic theorizing to question depression's standing as a disease, that's news. But when the world's leading public health organization, using a quite strict definition of illness, announces that depression has become the leading cause of disability in our hemisphere - you can scour the pages of the press and find nary a report.
