The landmark study is described in four papers that document the prevalence and severity of specific mental disorders. The papers provide significant new data on the impairment -- such as days lost from work -- caused by specific disorders, including mood, anxiety, and substance abuse disorders. These measures will allow researchers to determine the degree of disability and the economic burden caused by mental illness, as well as trends over time.
The papers are reported in the June 6 issue of the Archives of General Psychiatry by Ronald Kessler, Ph.D., and colleagues. The study was a collaborative project between Harvard University, the University of Michigan, and the NIMH Intramural Research Program.
This study, called the National Comorbidity Survey Replication (NCS-R), is a household survey of 9,282 English-speaking respondents, age 18 and older. It is an expanded replication of the 1990 National Comorbidity Survey, which was the first to estimate the prevalence of mental disorders (using modern psychiatric standards) in a nationally representative sample. The expansion includes detailed measures that will significantly improve estimates of the severity and persistence of mental disorders, and the degree to which they impair individuals and families, and burden employers and the U.S. economy.
"These studies confirm a growing understanding about the nature of mental illness across the lifespan," says Thomas Insel, M.D., Director of the National Institute of Mental Health. "There are many important messages from this study, but perhaps none as important as the recognition that mental disorders are the chronic disorders of young people in the U.S."
Prevalence and Age-of-Onset of Mental Disorders
Unlike most disabling physical diseases, mental illness begins very early in life. Half of all lifetime cases begin by age 14; three quarters have begun by age 24. Thus, mental disorders are really the chronic diseases of the young. For example, anxiety disorders often begin in late childhood, mood disorders in late adolescence, and substance abuse in the early 20's. Unlike heart disease or most cancers, young people with mental disorders suffer disability when they are in the prime of life, when they would normally be the most productive.
The risk of mental disorders is substantially lower among people who have matured out of the high-risk age range. Prevalence increases from the youngest group (age 18-29) to the next-oldest age group (age 30-44) and then declines, sometimes substantially, in the oldest group (age 60 +). Females have higher rates of mood and anxiety disorders. Males have higher rates of substance use disorders and impulse disorders.
The survey found that in the U.S., mental disorders are quite common; 26 percent of the general population reported that they had symptoms sufficient for diagnosing a mental disorder during the past 12 months. However, many of these cases are mild or will resolve without formal interventions.
It is likely, however, that the prevalence rates in this paper are underestimated, because the sample was drawn from listings of households and did not include homeless and institutionalized (nursing homes, group homes) populations. In addition, the study did not assess some rare and clinically complex psychiatric disorders, such as schizophrenia and autism, because a household survey is not the most efficient study design to identify and evaluate those disorders.
Failure and Delay in Initial Treatment Contact
The study documents the long delays between the onset of a mental disorder and the first treatment contact, as well as the accumulated burden and hazards of untreated mental disorders.
These pervasive delays in getting treatment tend to occur for nearly all mental disorders, though they vary according to specific diagnostic categories. The median delay across disorders is nearly a decade; the longest delays are 20-23 years, for social phobia and separation anxiety disorders. This is possibly due to the relatively early age of onset and fears of therapy that involve social interactions.
Shorter delays between onset of disorder and treatment seeking -- still a protracted 6-8 years -- are seen for mood disorders, and are likely attributable to public awareness campaigns, the marketing of newer therapies directly to consumers, and expanded insurance coverage.
While approximately 80 percent of all people in the U.S. with a mental disorder eventually seek treatment, there are public health implications from such long delays in treatment. Untreated psychiatric disorders can lead to more frequent and more severe episodes, and are more likely to become resistant to treatment. In addition, early-onset mental disorders that are left untreated are associated with school failure, teenage childbearing, unstable employment, early marriage, and marital instability and violence.
"The pattern appears to be that the earlier in life the disorder begins, the slower an individual is to seek therapy, and the more persistent the illness," said Dr. Kessler, a professor of health care policy at Harvard Medical School. "It's unfortunate that those who most need treatment are the least likely to get it."
Treating cases early could prevent enormous disability, before the illness becomes more severe, and before co-occurring mental illnesses develop, which only become more difficult to treat as they accumulate, according to the researchers.
Severity and Comorbidity of Mental Disorders
The second paper reports that even though mental disorders are widespread throughout the population, the main burden of illness is concentrated in those with a severe disorder - about 6 percent. A "serious" disorder involves a substantial limitation in daily activities or work disability, or a suicide attempt with serious lethal intent, or psychosis. The serious group reported a mean of 88.3 days -- nearly 3 months of the year -- when they were unable to carry out their normal daily activities.
Unfortunately, say the researchers, individuals with one mental disorder are at a high risk for also having a second one (comorbidity). Nearly half (45 percent) of those with one mental disorder met criteria for two or more disorders, with severity strongly related to comorbidity. This finding supports the suggestion by a growing portion of researchers that the boundaries between some diagnostic categories may be less discrete than previously believed.
Use of Mental Health Services
The study indicates that the U.S. mental health care system is not keeping up with the needs of consumers and that improvements are needed to speed initiation of treatment as well as enhance the quality and duration of treatment. For instance, over a 12-month period, 60 percent of those with a mental disorder got no treatment at all.
The good news is that the proportion of people who reported 12-month mental health service use is higher now - at 17 percent - than a decade ago in the baseline NCS survey, at 13 percent. The expansion was mainly in the general medical sector, with more primary care physicians providing psychiatric services.
People with mental or substance abuse disorders were more likely to get treatment from a primary care physician/nurse or other general medical doctor (22.8 percent), or from a non-psychiatrist mental health specialist (16 percent), such as a psychologist, social worker, or counselor, than from a psychiatrist (12 percent), though the survey did show that the adequacy of treatment -- measured by number of visits -- is best when provided by mental health practitioners. About 9.7 percent sought help from a counselor or spiritual advisor outside of a mental health setting; and 6.9 percent used a complementary-alternative source, such as a chiropractor or self-help group. This held true even for those with severe mood disorders. Traditionally underserved groups, such as the elderly, racial/ethnic minorities and those with low income or without insurance, had the greatest unmet need for treatment.
Future and Ongoing Efforts
The NIMH epidemiological research portfolio contains several related projects that are focused on mental disorders among adolescents and ethnic subgroups. These include 1) an arm of the NCS-R that is studying 10,000 youths; 2) the National Study of African American Life, with 6,000 participants; and 3) the National Study of Latino and Asian Americans, with 5,000 participants. Each of these, like the NCS-R, will provide information on diagnosis, medications, disability/impairment, and service use, drawing from nationally based samples.
An international perspective on these findings is also becoming available, as the study is part of a global initiative on the epidemiology of mental disorders in 28 countries, coordinated through the World Health Organization.
NIMH is part of the National Institutes of Health (NIH), the Federal Government's primary agency for biomedical and behavioral research. NIH is a component of the U.S. Department of Health and Human Services.