Prevalence and Severity of Mental Illness In The United States

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Mental Disorders

Over the course of the previous 12 months, more than one-fourth of adults reported having symptoms that would qualify them for a diagnosis of a mental disorder; and most of those disorders can be classified as serious or moderate, according to a study in the June issue of the Archives of General Psychiatry, one of the JAMA/Archives journals.

Although previous epidemiological surveys have estimated prevalence of mental disorders in the U.S. as high as 30 percent, information on severity and comorbidity (individuals with symptoms that meet criteria for two or more mental disorders at the same time) has not previously been available, according to background information in the article.

Ronald C. Kessler, Ph.D., of Harvard Medical School, and colleagues analyzed information on mental disorders in the United States collected from the U.S. National Comorbidity Survey Replication (NCS-R), a nationally representative face-to-face household survey conducted between February 2001 and April 2003 using the World Health Organization World Mental Health Survey Initiative version of the Composite International Diagnostic Interview. The researchers determined the 12-month prevalence of different types of mental disorders (the percentage of individuals reported having symptoms that would represent a particular mental disorder in the course of the previous 12 months) as well as the level of severity of the disorder in that 12-month period and the likelihood that an individual qualifying in that 12-month period for a diagnosis for one mental disorder would also meet the criteria for at least one other (comorbidity).

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The disorders were divided into four classes: anxiety disorders, including panic disorder, post-traumatic stress disorder and obsessive-compulsive disorder; mood disorders, including major depressive disorder and bipolar disorder; impulse control disorder, including oppositional defiant disorder, attention deficit/hyperactivity disorder and intermittent explosive disorder; and substance abuse disorder, defined as alcohol and drug abuse and dependence. Severity was divided into three levels: serious, which might be defined by criteria including a serious suicide attempt or substantial work limitations as result of the disorder; moderate, which might defined by criteria including suicide ideation or substance abuse without serious impairment of functioning; and mild.

Based on data obtained from 9,282 adult respondents to the survey, the researchers determined that the 12-month prevalence for any disorder was 26.2 percent, with a 12-month prevalence of anxiety disorders of 18.1 percent; mood disorders, 9.5 percent; impulse control disorders, 8.9 percent and substance abuse disorders, 3.8 percent. Of the cases, 22.3 percent were classified as serious; 37.3 percent as moderate and 40.4 percent as mild. Fifty-five percent of individuals with a disorder met the criteria for only one disorder, 22 percent for two diagnoses and 23 percent for three or more diagnoses.

"Although mental disorders are widespread, serious cases are concentrated among a relatively small proportion of cases with high comorbidity," the authors conclude.

(Arch Gen Psychiatry. 2005;62:617-627) - Chicago

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