Nearly one-half of all Americans between the ages of 15 and 54 have experienced an episode of psychiatric disorder at some time in their lives, and nearly 30 percent have had such an episode at some time in the last year, according to the first national survey to administer psychiatric interviews to a sample of the general population.
A number of regional studies have been carried out over the past decade, but they found lower estimates than this nationally representative survey, says sociologist Ronald C. Kessler, the principal investigator of the study, which appears in the current (January 1994) issue of the Archives of General Psychiatry.
The most common disorders identified in the study, conducted through the Institute for Social Research (ISR): major depression, with 17 percent of the population experiencing an episode at some time in their lives and over 10 percent in the last year; and alcohol dependence, with 14 percent experiencing a problem at some time in their lives and more than 7 percent in the last year.
The next most common disorders are social phobias, such as extreme fear of speaking in public or meeting new people, and simple phobias, such as fear of flying, with 13 percent and 11 percent, respectively, of the population experiencing the disorders in their lives, and 8 percent and 9 percent, respectively, in the last year.
The survey found that severity is strongly associated with the number of disorders. In particular, the roughly one-fourth of lifetime cases who have a history of several different co-occurring disorderssuch as anxious depression with co-occurring alcohol dependenceaccount for close to 90 percent of the severe recent disorders in the total population.
The survey was funded by the National Institute of Mental Health, the National Institute of Drug Abuse, the National Institute of Alcohol and Alcohol Abuse, the W.T. Grant Foundation, and the John D. and Catherine T. MacArthur Foundation.
The study used a diagnostic interview to assess the mental health of a nationally representative sample of over 8,000 civilian, non-institutionalized persons. The interview was designed to identify disorders described in the most recent version of the Diagnostic and Statistical Manual of Mental Disorders of the American Psychiatric Association, the standard classification system used in the United States. Interviews were conducted between September 1990 and February 1992.
Among the key findings:
It is important, according to Kessler, not to conclude that all those who have had a psychiatric disorder at some time in their lives need psychiatric treatment. Just as there is wide variation in the severity of physical illnesses, so too with psychiatric disorders. Many psychiatric disorders cause only minor impairment and resolve without treatment.
Nonetheless, he adds, psychiatric disorders can cause great pain and suffering and it is important that people with these disorders have access to treatment. This is not universally true in the United States today.
Among other conclusions:
While psychiatric disorders are widespread, the most severe of these disorders are concentrated among the much smaller number of people who have a lifetime history of several co-occurring disorders. These people constitute less than 15 percent of the population and, within a given year, the subgroup of these people currently having disorders severe enough to require treatment is estimated at between 3 percent and 5 percent of the total population.
Kesslers U-M co-authors are ISR colleagues Katherine A. McGonagle, Shanyang Zhao, Christopher B. Nelson and Suzann Eshleman.