One-quarter of all Americans met the criteria for having a mental illness within the past year, and fully a quarter of those had a "serious" disorder that significantly disrupted their ability to function day to day, according to the largest and most detailed survey of the nation's mental health, published yesterday.
Although parallel studies in 27 other countries are not yet complete, the new numbers suggest that the United States is poised to rank No. 1 globally for mental illness, researchers said.
"We lead the world in a lot of good things, but we're also leaders in this one particular domain that we'd rather not be," said Ronald Kessler, the Harvard professor of health care policy who led the effort, called the National Comorbidity Survey Replication.
The exhaustive government-sponsored effort, based on in-depth interviews with more than 9,000 randomly selected Americans, finds that the prevalence of U.S. mental illness has remained roughly flat in the past decade -- a possible glimmer of hope given that previous decades had suggested the rates were gradually rising.
But the rest of the news from the survey -- which did not include some of the most serious disorders, such as schizophrenia, for which patients are often institutionalized -- is mostly discouraging.
Less than half of those in need get treated. Those who seek treatment typically do so after a decade or more of delays, during which time they are likely to develop additional problems. And the treatment they receive is usually inadequate.
Younger sufferers are especially overlooked, the survey found, even though mental illness is very much a disease of youth. Half of those who will ever be diagnosed with a mental disorder show signs of the disease by age 14, and three-quarters by age 24. But few get help.
Many factors contribute to these failings, the reports conclude, including inattention to early warning signs, inadequate health insurance and the lingering stigma that surrounds mental illness.
"The system has to get its act together to get its quality of care up," Kessler said.
Thomas Insel -- chief of the National Institute of Mental Health, which funded the $20 million study -- said the nation needs to recognize that mental illness is a chronic condition that requires expert medical attention just as heart disease, Alzheimer's and diabetes do.
He said he was disappointed to learn from the survey that despite the availability of effective treatments for many mental illnesses, including depression and anxiety, about a third of people in need rely solely on nonprofessional sources such as Internet support groups and spiritual advisers.
"You wouldn't rely on your priest for treatment if you had breast cancer," Insel said. "Why would you go to your priest for a major depressive disorder? These are real medical and brain disorders, and they need to be treated that way."
Mental health surveys have been conducted nationwide since the 1940s, but they offered only crude measures until 10 years ago, when the first National Comorbidity Study was performed. That highly structured survey asked questions specific enough to provide an accurate diagnosis for a wide range of mental disorders.
The study's 10-year follow-up, described in four reports in the June issue of the Archives of General Psychiatry, goes further by measuring, for the first time, the severity and persistence of people's mental illness and the quality of their treatment.
The survey, conducted by the University of Michigan, included 9,282 households selected at random in 34 states. Nearly 300 trained interviewers traveled about 8 million miles over a year and a half. They knocked on doors at all hours of the day and night to ensure they would not systematically miss alcohol abusers who spend their days at bars, people with depression who can go weeks hardly able to pull themselves out of bed and people with social phobia who only rarely answer the doorbell.
The interview notes were uploaded to a central repository for analysis by psychiatrists and other health professionals at Harvard Medical School.
The survey focused on four major categories of mental illness: anxiety disorders (such as panic and post-traumatic stress disorders); mood disorders (such as major depression and bipolar disease); impulse control disorders (such as attention-deficit/hyperactivity disorder); and substance abuse.
Almost half of Americans meet the criteria for such an illness at some point in their lives, the survey found. Most cases are mild and probably do not require treatment. But every year about 6 percent of adults are so seriously affected that they cannot perform even routine activities for periods averaging three months. Because schizophrenia, autism, and some other severe and relatively common disorders were not included, actual prevalence rates are somewhat higher, Kessler said.
Comorbidity -- the simultaneous occurrence of two or more illnesses -- is common, the survey found. Nearly half of people with one mental disorder met the criteria for two or more. That's a problem because mental health services are usually geared toward one illness or another.
"Our findings highlight the importance of integrating treatments, of treating the people instead of the disorder," said NIMH investigator Kathleen Ries Merikangas.
The fraction of the population treated for mental illness over a 12-month period has grown to 17 percent from 13 percent a decade ago -- a sign, perhaps, that advertisements for antidepressants and other drugs are working, and the stigma of being treated is decreasing.
But most of those affected receive either no help or are being treated by nonmedical providers or nonspecialists, whose care typically fails to meet minimal standards of adequacy, Kessler said.
It is not clear why Americans have such high rates of mental illness, but cultural factors clearly play a role. Immigrants quickly increase their risk of mental health problems, especially if they do not live in native ethnic communities. Minorities also tend to have lower levels of mental health problems despite lower economic status, suggesting that the social support they provide each other is protective.