As you took the test you probably realized you or someone you love suffers recurrently from this all-too-common malady. It is by no means surprising that almost everyone, even if he is not depressed, knows someone who is, for the United States is experiencing an unparalleled epidemic of depression. Dr. Gerald Klerman, when he was the director of the U.S. government’s Alcohol, Drug Abuse and Mental Health Agency, coined the apt term “The Age of Melancholy” to describe our era.

In the late 1970s, Klerman sponsored two major studies of the rate of mental illness in America and the findings were startling. The first, called the ECA (epidemiological catchment area) Study, was designed to find out how much mental illness, of every kind there is in the United States. Researchers visited and interviewed 9,500 people who were randomly picked to be a cross section of adult Americans. They were all given the same diagnostic interview that a troubled patient who walks into a knowledgeable psychologist’s or psychiatrist’s office would get.

Because such an unusually large number or adults of different ages were interviewed, and asked if and when they had experienced major symptoms, the study gave an unprecedented picture of mental illness over many years and made it possible to trace the changes that had taken place over the course of the twentieth century. One of the most striking changes was in the so-called lifetime prevalence of depression—that is, in the percentage of the population that has been depressed at least once in their lifetime. (Obviously, the older you are the more chance you have had to get any given disorder. The lifetime prevalence of broken legs, for instance, goes up with age, since the older you are, the more opportunities you have had to break a leg.)

What everyone who was interested in depression expected was that the earlier in the century a person was born, the higher would be the person’s lifetime prevalence of depression—that is, the more episodes of depression he would have had. If you’d been born in 1920, you’d have had more chances to suffer depression than if you’d been born in 1960. Before they saw the findings, medical statisticians would have stated that if you were twenty-five years old at the time you were interviewed for the study—if, that is, you were born around 1955—there was about a 6 percent chance you’d had at least one instance of severe depression, and if you were between twenty-five and forty-four years old, your risk of acute depression would have climbed—say, to about 9 percent—as any sensible cumulative statistic should.

When the statisticians looked at the findings, they saw something very odd. The people born around 1925—who, since they were older, had had more chance to get the disorder—hadn’t suffered much depression at all. Not 9 percent but only 4 percent of them had had an episode. And when the statisticians looked at the findings for people born even earlier—before World War I—they found something even more astounding. Again, the lifetime prevalence had not climbed, as one would have thought; it nosedived to a mere 1 percent.

These findings were probably not artifacts of forgetting or reporting biases. So this suggests that people born in the middle third of the century are ten times likelier to suffer depression than people born in the first third. One study, however—even one done as well as the ECA Study—does not entitle scientists to shout “Epidemic.” Fortunately, the National Institute of Mental Health had done another study, called the Relatives Study, at the same time. It was similar to the ECA Study in design, and it too covered a considerable number of people. This time the people weren’t randomly selected; they were chosen because they had close relatives who had been hospitalized for severe depression. The questioners started with 523 people who had already been severely depressed. Almost all the readily available first-degree relatives of these people—a total of 2,289 fathers, mothers, brothers, sisters, sons, and daughters—received an identical diagnostic interview. The aim was to find out if these relatives had ever been seriously depressed too, to see if relatives of seriously depressed people are at greater risk of depression than the population at large. Knowing this would help untangle the genetic from the environmental contribution to depression.

Again, as in the ECA Study, the findings turned expectations upside down. They showed a greater than tenfold increase in depression over the course of the century.

Consider just the women. Those studied who had been born during the Korean War period (which means they were about thirty years old at the time of the ECA Study) were ten times likelier to have had an episode of depression than women born around World War I were, even though the older women (in their seventies at the time of the study) had had much more opportunity to become depressed.

Back when the women of the World War I generation were thirty (the age the Korean War women now were), only 3 percent of them had had a severe depression. Contrast this with the fate of the women of the Korean War period: By the time they were thirty, 60 percent of them had been severely depressed—a twentyfold difference.

The statistics on the males in the study showed the same surprising reversal. Though the men suffered only about half as much depression as the women …, the percentage of men who had been depressed displayed the same strong increase over the course of the century.

Not only is severe depression much more common now; it also attacks its victims much younger. If you were born in the 1930s and later had a depressed relative, your own first depression, if you had one, would likely strike between the ages of thirty and thirty-five. If you were born in 1956, your first depression would probably strike when you were between twenty and twenty-five—ten years sooner. Since severe depression recurs in about half of those who have had it once, the extra ten years of vulnerability to depression add up to an ocean of tears.

And there may be other oceans, for these studies are concerned only with severe depression. Milder depression, which so many of us have experienced, may show just the same trend: There may be a great deal more of it than there used to be. Americans, on average, may be more depressed, and at a younger age, than they have ever been: unprecedented psychological misery in a nation with unprecedented prosperity and material well-being.

In any case, there is more than enough to warrant shouting “Epidemic.”