Two major grants to clarify, coordinate research on children's mental health

January 3, 2000

The National Institute of Mental Health has awarded two grants, totaling more than $4 million, to the University of Chicago and the National Opinion Research Center to obtain data that can resolve differences among the several competing systems of diagnostic classification used to describe children's mental health problems.

The lack of common terminology has been a major stumbling block for research in the field, hampering cooperation between research teams and comparison of related studies.

"Researchers who study children's mental health problems currently labor in a veritable tower of Babel," explains Benjamin Lahey, PhD, professor of psychiatry at the University of Chicago and principal investigator on both grants. "Different researchers speak widely varied professional languages as they try to define mental health diagnoses and measure symptoms."

Because these varying diagnostic languages rely on different "words" (symptoms and other diagnostic criteria) and "syntax" (rules for putting together the symptoms to define syndromes), the results of studies using one diagnostic language often cannot be combined with findings from studies using another diagnostic language, explains Lahey.

The dominant diagnostic language for child and adolescent psychiatrists in the United States is that of the American Psychiatric Association's Diagnostic and Statistical Manual. However, the symptoms and diagnostic criteria for children's mental disorders in this manual have been revised many times in recent years, "often without adequate empirical justification," notes Lahey, "resulting in considerable confusion."

Adding to the mix, mental health researchers outside of the United States often use the International Classification of Diseases. Although the symptoms of mental disorders of children and adolescents used in these two diagnostic manuals were brought into agreement in the most recent editions of these manuals, the syndromes of child and adolescent mental disorder are defined in very different ways.

Complicating matters further, many mental health researchers shun both manuals and use instead various mental health rating scales. These scales assess mental health problems using sets of symptoms that only partially overlap with the standard manuals and they define the syndromes of mental disorder in ways that are often quite different from the two diagnostic manuals.

The two NIMH-supported studies will collect data to resolve these differences. "We expect," said Lahey, "that a new diagnostic nomenclature for children's mental health will emerge that combines the most valid symptoms and diagnostic rules from each of several current systems."

Both studies will use a new interview instrument designed to obtain information from children and adolescents, their parents, and their teachers on the symptoms of a child's mental disorder. The new instrument includes all of the non-overlapping symptoms measured in all of the competing nomenclatures.

In the first study, interviewers from Research Triangle Institute, in North Carolina, will administer the interview to 1,400 children and adolescents selected to be representative of all youth living in Atlanta, Georgia, and the surrounding suburban and rural counties. The responses to questions about mental health symptoms will be analyzed using statistical techniques that identify clusters of co-occurring symptoms.

"Because no one has ever looked at all of these symptoms together, new syndromes will likely emerge," says Lahey.

Information obtained in this first study will allow researchers to examine the correlations of each putative syndrome with measures of impaired functioning in important areas of life, such as problems with peers or difficulties in school, as well as with suspected risk factors for mental disorders, such as unusual parenting practices.

In the second study, researchers from the National Opinion Research Center at the University of Chicago will administer the same interview to a sample of 2,000 twin children and adolescents.

This second study will directly compare the fit of a variety of hypotheses regarding the syndromes of mental disorder to the data, testing each existing taxonomic nomenclature and any new hypotheses emerging from the first study. Because no one has ever collected data on all symptoms used in all of the major mental health nomenclatures from the same youths, this will be the first time that this critical comparative test has been conducted.

The data from the twin study will also provide estimates of relative importance of genetic and environmental influences on each hypothesized syndrome. About half of the twins will be monozygotic--virtually identical genetically. The remaining subjects will be dizygotic--no more genetically similar than siblings. Each set of twins, however, will have been raised under very similar conditions.

Information on genetic and environmental influences provides a powerful tool to choose between "lumping" two correlated syndromes into a single syndrome versus "splitting" them into separate syndromes. "If two syndromes that tend to co-occur share the same genetic and environmental influences, they probably should be lumped together," explains Lahey, "but if they have distinct genetic or environmental influences, they probably should be split into separate dimensions."

"The twin data will allow a statistical modeling of the genetic co-variation among symptoms, bringing us closer to a description of the mental health phenotypes that have the strongest genetic influences," adds Lahey.

"If these studies can lead to a common diagnostic language for researchers and clinicians, it will greatly improve researchers' ability to work together to understand mental health problems," he concludes. "Until we have an agreed-upon, empirically based taxonomy, we cannot hope to unravel the genetic and environmental influences on child mental health problems."

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