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Take the population of Texas: almost 22 million.
Throw in Oklahoma and Louisiana. Add Arkansas and New Mexico and you have around 34 million people in all, approximately how many Americans will suffer severe and debilitating depression sometime in their adult lives.
New research, published Wednesday in The Journal of the American Medical Association, documents the staggering scope of depression in the United States, as well as its impact on job productivity. One study in the journal, which this week focuses on depression, estimates that the illness costs employers an extra $31 billion a year in lost productivity - or almost $4 billion more than the entire year's budget for the National Institutes of Health.
"Depression is more common than we thought. It's more chronic than we thought. It's more recurrent than we thought. It's more disabling than anyone had imagined," said Dr. A. John Rush, an author of the study gauging the extent of profound depression in the U.S. population.
That study, an in-person survey of more than 9,000 adults, determined that 16.2 percent of Americans will suffer major depressive disorder in their lifetime, and that 6.6 percent had the illness within the previous year.
While there have been other estimates in the past about the extent of depression in the population, "this is certainly the best one to date," said Dr. Andrew Young, a psychiatrist with the Department of Veterans Affairs and the Neuropsychiatric Institute at the University of California, Los Angeles. Many of those studies have gauged depression's prevalence among people in health-care settings, he added, but the new study is set in the general population.
"This is sort of the last word in terms of prevalence," he said.
Although slightly more than half of those who had major depression in the last year had pursued medical treatment, only about 42 percent of them received treatment the study deemed adequate. That means that more than three-quarters of those who struggled with severe depression in recent months didn't receive proper treatment, the study showed.
"Suffice it to say only roughly a third of people with major depression receive treatment," said Young, whose own studies of health-care services have found such treatment deficiencies. "With any other disorder, there'd be a national outcry about it."
However, the study, led by Ronald Kessler of Harvard Medical School, couldn't discern how many people actually benefited from any level of treatment, Rush added. On average, bouts with severe depression last 16 weeks, the researchers found.
In the study of lost worker productivity, scientists at AdvancePCS, a pharmacy benefit management company, found that workers with depression reported far more lost productive time because of various physical health complaints than the expected rate for workers without depression. (Lost time included time missed from work as well as time not spent productively at work - which actually accounted for more lost time.)
On average, workers with depression lost 5.6 hours of productive time a week, compared with an expected rate of 1.5 hours for nondepressed workers.
Depression's workplace impact was larger than the scientists had initially expected, said lead researcher Walter Stewart, now director of outcomes research at Geisinger Health Systems, a health-care company. But the finding makes sense, he said.
"When you look at depression, while it's not the most common illness in the workplace, the one thing that does distinguish it from other health problems is that when people are in episodes of depression, they do last for a relatively long time," he said. By comparison, migraine attacks are also disabling but last only a few days.
In all, the study found that 9.4 percent of the U.S. workforce had any depressive disorder during a given two-week period. (Most common was a low-grade, chronic depression known as dysthymia.) And any type of depression was almost twice as common in women as in men, the study found.
"If you have an all-female workforce, it's not 9 percent, it's 12 percent. If you have an all-male workforce, it's 6 percent," Stewart said.
The productivity study is the strongest and most detailed such study he's seen, said Young, an associate professor at UCLA. "It's an important one because we've known for quite some time that depression impairs work productivity, but in terms of how and how much, there's really been a lot of uncertainty."
The issue is vital from a public policy standpoint, he said, because society wants to treat disorders that cause a substantial economic impact. Because employers stand to benefit, he added, such research helps make a strong case for equity between mental health and physical health insurance benefits.
The broader study of U.S. depression, meanwhile, gave a clear picture of the illness' severity, too, Rush said. "When you pick up these depressive symptoms in the population this isn't a couple of days where you just feel blue," he said. "The vast majority of these cases are not even in the mild range." The study found that almost 90 percent of the depression cases within a year were classified as moderate, severe or very severe.
Those with major depression averaged more than 35 days in the previous year during which they were totally unable to carry out normal activities, the study found. For most chronic conditions, other research has found, the average is less than 15 days.
"The more severely depressed you are, the more disabled you are, and the longer you're going to be depressed," Rush said.
In addition, more than half of those who had suffered major depression also had an anxiety disorder such as panic or post-traumatic stress disorder. In most of those cases, the anxiety preceded the depression, Rush said. "So the first message is, today's anxiety may be tomorrow's depression."
Like previous research, the new study found that the more recently people had been born, the more likely they were to have depression arise early in their lives. The reason for the declining age of onset has mystified researchers. "Is it stuff in the water supply, is it the media, is it the tax code, is it what you eat, lack of exercise, getting fat?" Rush asked.
Ultimately, Young said, the importance of such studies is any long-term effects they have. Particularly crucial is dispelling the stigma that keeps people from getting proper diagnoses and treatment, he said, and in building support to ensure care for even the most disadvantaged, who are particularly plagued by mental ills.
"We've seen information like this before. And nothing really has come of it from a national perspective, in terms of improving access to mental health services and insurance coverage, and changing stigma," he said. "The real question is, What can be done to improve care?"
(c) 2003, The Dallas Morning News. Distributed by Knight Ridder/Tribune News Service.