"To our knowledge, this is the first [such] published report," writes lead researcher Frank P. MacMaster, a psychiatric researcher with the National Research Council in Halifax, Canada.
Major depressive disorder is just as common in adolescence as it is in adulthood, he explains. By studying younger patients, he hoped to see brain structure differences that could cause the disorder.
Because patients were young and had not yet been treated for depression, the effects of long-term illness or treatment would not affect the images, he explains.
In their study, MacMaster and colleagues from Dalhousie University studied 34 adolescents between ages 13 and 18, half of whom were suffering from major depressive disorder. Using highly sensitive MRI, they obtained brain scans of each teen and measured the volume of their left and right hippocampus.
Teens with major depression had 17% smaller hippocampus volume than the control group, reports MacMaster.
Males had more prominent hippocampus differences than did females, a finding that matches an earlier study, he notes.
Also, patients whose major depression had lasted longer had larger hippocampuses than the more recently diagnosed patients. This may indicate either a change related to duration of illness or the brain's attempt to normalize, he writes.
In other studies, cell death in the hippocampus has been linked with the number of days depressed, MacMaster adds.
His study appears in the recent issue of the journal BioMed Central Medicine.
SOURCE: MacMaster, F. BioMed Central Medicine, January 2004.