Studying Mental Health: Categories or Dimensions?
Experts say that elements of both psychiatry and psychology should be considered when studying mental health.
Published June 1, 2003
By Vida Foubiste
Academy Contributor

One of the dichotomies between basic and clinical research into childhood mental illness has been the nomenclature of classification. Psychiatrists have historically used “categories” to classify neurological disorders; psychologists have turned to “dimensions.”
Thus, the Roots of Mental Illness in Children and Adolescents conference organizers set out to find a keynote speaker who could bridge this sometimes “cavernous gap,” said Doreen S. Koretz, chief of the Developmental Psychopathology and Prevention Research Branch, Division of Mental Disorders, Behavioral Research and AIDS, at the National Institute of Mental Health, Bethesda. The conference was supported by The New York Academy of Sciences (the Academy).
They turned to Sir Michael Rutter, MD, F.R.S., professor of Developmental Psychopathology at the Social, Genetic and Developmental Psychiatry Research Centre, Institute of Psychiatry, in London, and a leading expert in child psychiatric research.
By his own admission, Sir Michael took a rather “British approach” and, one by one, challenged “meta-theoretical claims” behind the two approaches. “The battle, as it has sometimes been, between dimensional and categorical approaches is rather futile,” he admitted. Ultimately, both are necessary.
Among the claims he challenged to reach that conclusion were:

Dimensional analyses have greater statistical power. But, says Sir Michael, odds ratios can sometimes be preferable. A recent study using Canadian data, for example, found no difference between maternal care and group day care on physical aggression in children ages two and three — except when the children came from families at high psychosocial risk. “Where there was high family risk, the rates of aggression were substantially higher among those receiving family home care,” he said.
Another assumes that the most important environmental influences are outside the family and only extreme environments have any effects of functional importance. “Both are demonstrably false,” said Sir Michael. A French study has shown that children removed from their parents because of abuse or neglect and then adopted between the ages of four and six-and-a-half have a rise in IQ at adolescence, the degree of which is systematically related to the socio-educational level of the adoptive homes. “These are differences within the relatively narrow range of adoptive homes,” he explained.
A further wrong assumption is that causal inferences can be partitioned into those that are genetically or environmentally mediated, with their summation amounting to 100 percent of effects. One example of the shortcoming of this claim is the role that people themselves play in selecting and shaping their environment. A longitudinal study of girls at age 10 with anti-social behavior found that, in the absence of marital support, there is a high degree of persistence 18 years later. “But, given marital support, there is a huge improvement in social functioning,” said Sir Michael.
“There’s an American saying, which says something like, ‘It ain’t ignorance that does the harm, it’s knowing too many things that ain’t true,’” Sir Michael said. “I’m a great believer in that.”
Also read: Mental Health in Children and Adolescents