TUESDAY, Feb. 19, 2002 (HealthDayNews) -- Researchers have found children and adolescents with major depressive disorder (MDD) who do not have a family history of the disease have larger brains than MDD patients who have relatives with the condition.
The study, which appears in the February issue of Archives of General Psychiatry, says the left prefrontal cortex (LPFC) section of the brain was larger in children and teen-agers with non-familial MDD than in patients who had at least one family member with the same disease. Their brains were also bigger than the ones in control subjects who did not have MDD.
"There appeared to be different types of brain patterns in children with MDD who have a familial history," says study author Carla Nolan, who did the research at Wayne State University and who is now a graduate student in psychology at Emory University. "It's definitely depression, but there seem to be two distinct subgroups."
Although the findings are preliminary, they could one day help point to more effective treatments, if indeed the causes are different for each subgroup.
However, another expert finds the results a bit perplexing.
"I find it strange that non-familial MDD subjects would be singled out as having larger LPFC," says Stephen Hanson, chairman and associate professor of the psychology department at Rutgers University. "If there was a developmental component to this anatomical difference, it would seem more likely related to genetic influences, again suggesting that familial MDD subjects would be singled out as an anatomical anomaly -- not non-familial MDD subjects."
According to the study authors, about 15 percent to 20 percent of children and teen-agers develop MDD. The same prevalence occurs in adults, suggesting that, without intervention, children with MDD grow up to be adults with MDD.
The prefrontal cortex region of the brain undergoes substantial changes during childhood and adolescence. Because abnormalities in the prefrontal cortex have been noted in people with MDD, the researchers have hypothesized this might contribute to the onset of the disease.
The researchers thought that looking at that section of the brain in younger patients who were not on psychotropic medications might clarify the role of this region of the brain in development of MDD.
Nolan and her colleagues assessed the severity of symptoms and performed magnetic resonance imaging (MRI) scans of the brains of 22 MDD patients between 9 and 17 years of age. None had taken any psychotropic medications. Of these, 12 had familial MDD, while 10 had no clear family history of the disease. The control group was 22 patients without MDD.
As it turns out, the left prefrontal cortical volumes of the participants with non-familial MDD were 17 percent larger than the patients with familial MDD, and 11 percent larger than the controls.
As the size of LPFC decreased in children with MDD in the familial group, the severity of symptoms increased. There didn't appear to be any association between severity of symptoms and size of LPFC in the non-familial group.
The study has some significant limitations. For one thing, the sample size was tiny, only 22 subjects, not counting controls. There's also some debate as to what the prefrontal cortex actually does.
"I think function mapping in the brain is so poorly understood at this point that a size difference in cortical structure, no matter how reliable, is very difficult to define at this time," Hanson says.
What To Do: The National Institute of Mental Health and the National Alliance for the Mentally Ill have information about childhood depression.
