Mental illness prevalence rates in the United States far surpass those of a number of countries in Europe, Asia, and the Middle East, according to data released by the World Health Organization (WHO) in June.

Furthermore, as many as three-quarters of survey respondents with serious mental health problems in some countries may not be receiving treatment, the WHO study found.

The data are the first from a series of surveys by the WHO World Mental Health Consortium; they appeared in the June 2 Journal of the American Medical Association.

As part of the worldwide initiative, trained lay interviewers in 14 countries conducted face-to-face interviews with randomly selected household samples ranging in size from 1,663 people in Japan to 9,282 people in the United States, for a total of 60,463 respondents. The surveys were conducted from 2001 through 2003.

Researchers used the World Mental Health-Composite International Diagnostic Interview (CIDI) and DSM-IV to assess whether respondents had any of the following: anxiety disorders; mood disorders; disorders that share a feature of impulse control such as bulimia, intermittent-explosive disorder, attention deficit-hyperactivity disorder, conduct disorder, and oppositional defiant disorder; and substance use disorders.

The survey was translated into each country's official language.

The disorders were classified as serious, moderate, or mild.

Respondents who had bipolar I disorder, drug dependence with a physical-dependence syndrome, those who had made a suicide attempt, those who reported severe role impairment due to a mental disorder on the Sheehan Disability Scales, or those who scored 50 or lower on the Global Assessment Functioning Scale due to a mental disorder were judged by researchers to have serious mental disorders.

Disorders were classified as moderate if role impairment from a mental disorder was moderate in any Sheehan Disability Scales domain or if the respondent had substance dependence without a physiological dependence syndrome.

All other disorders were classified as mild.

Researchers also determined whether respondents received treatment for" problems with emotions, nerves, mental health, or use of alcohol or drugs" from a mental health professional, general medical professional, religious counselor, or traditional healer during the prior year.

According to the findings, respondents in the United States had the highest prevalence rates of mental illness (26.4 percent). Ukraine showed the second highest at 20.4 percent.

Researchers analyzing data from other corners of the world found the lowest mental illness prevalence rates in Shanghai, China (4.3 percent), Nigeria (4.7 percent), and Italy (8.2 percent).

Ukraine stood out as having the highest rates of substance use disorders (6.4 percent), while the United States was second, with rates of 3.8 percent.

U.S. residents had the highest rates of anxiety disorders (18.2 percent), and those living in Shanghai reported the lowest (2.4 percent).

Ronald Kessler, Ph.D., the primary investigator on the study, told Psychiatric News he believed that in some cases, figures relating to mental illness prevalence rates are "wild underestimates." Kessler is a professor of health care policy at Harvard Medical School.

A number of factors, he said, may have contributed to underreporting of mental illness in some areas such as Shanghai, for example. "There is an enormous amount of embarrassment related to these things—people don't talk about mental health problems, so our ability to get accurate and complete reports is compromised in some places."

Kessler offered an example. "In China, although we found low rates of mood disorders (2.5 percent), we know the suicide rates there are among the highest in the world—so it's inconceivable that the rates of depression are that low," he said.

In addition, unlike the United States, many countries lack a tradition of free speech. "The concept of anonymity doesn't exist in some places," Kessler said, leading to a greater reluctance to admit to emotional or substance abuse problems.

Attention to cultural idioms or expressions is essential for gathering accurate information about mental illness in different countries, Darrel Regier, M.D., M.P.H., director of the American Psychiatric Institute for Research and Education, pointed out.

Mental illness prevalence rates for certain disorders in Asian countries, in particular, may be underreported because the questions used to determine if respondents had depression, for instance, may not have been phrased in terms that would normally be used by people in those countries, he said.

In Korea or China, questions that might best elicit information about depression would be phrased to ask respondents if they felt uncomfortable, out of sorts, or that something wasn't right with their bodies, Regier said.

In countries throughout Asia, he noted, "there aren't even words to describe terms commonly used to describe depression in the Western hemisphere, such as sad or blue," he added.

Regier also noted that "one positive benefit of this study will be to use the striking difference in prevalence rates as a basis for examining different cultural expressions and the possible need for some culture-specific diagnostic criteria, to define worldwide homogeneous diagnostic groups for DSM-V and ICD-11."

Kessler acknowledged that problems with phrasing may have contributed in small part to underreporting, but stressed that he and his colleagues in each country were taking a "first stab" at trying to "get the words straight to describe what we mean by certain illnesses by using local idioms" in the survey questions. "This is a work in progress," he added.

The proportion of people who received treatment for mental disorders during the past year varied greatly from country to country, according to the findings—from 0.8 percent in Nigeria to a high of 15.3 percent in the United States.

But perhaps most striking was the finding that about half the respondents with serious mental disorders in developed countries such as the United States, Belgium, and the Netherlands received no treatment during the prior year.

In less-developed countries such as Ukraine, as many as 80 percent of those with serious mental disorders were not receiving treatment. Only 23.7 percent and 20 percent of those with serious mental health problems were receiving treatment in Colombia and Mexico, respectively.

However, while treatment seemed to evade many serious mental disorders in the United States, 23 percent of those considered to have mild disorders and 8 percent who did not meet criteria for a mental disorder—researchers called these "sub-threshold cases"—were receiving treatment.

In Western European countries such as Belgium, Spain, and Germany, the proportion of people with mild mental disorders who received treatment was even higher.

That many with mild mental health problems were receiving treatment while a significant number of those with more serious disorders were not led Kessler to conclude while there is not enough money being designated by governments to help people get treatment for mental health problems, "we could do a better job of reallocating the treatment resources we already have."

Just how to do that remains a mystery, Kessler admitted—especially in a decentralized health care system where in addition to disparities in socioeconomic status, factors such as education levels and culture play a role in why people seek treatment for mental health problems.

Kessler emphasized that putting more resources into prevention—screening children for anxiety and depression in schools and intervening with various treatments such as cognitive-behavioral therapy, for instance, may be helpful.

A number of organizations provided funding for the study, including the John D. and Catherine T. MacArthur Foundation, Pfizer Foundation, European Commission, and GlaxoSmithKline.

An abstract of the article, "Prevalence, Severity, and Unmet Need for Treatment of Mental Disorders in the World Health Organization World Mental Health Surveys" is posted online at<jama.amaassn.org/>.▪