"Researchers and clinicians have often raised the question of whether clinical depression is a state or a trait," said Lance O. Bauer, professor of psychiatry at the University of Connecticut School of Medicine and lead author of the study. "That is, do patients with clinical depression possess normal brain function that only becomes abnormal when they are in a state of active depression? Or, alternatively, do these patients possess a subtle brain abnormality which is always present, in other words, a trait?"
Researchers examined 151 adolescent females, 15 to 20 years of age, divided into six categories: depressed or nondepressed, those with a positive or negative family history of alcoholism, and those with a positive or negative family history of depression. Of the total, 58 met Diagnostic and Statistical Manual of Mental Disorders - Third Edition, Revised (DSM-IIIR) criteria for a personal lifetime diagnosis for depression (only 4 of these met the criteria for a current episode of depression). Researchers recorded electroencephalographic (EEG) activity from 31 electrode sites while the subjects sat relaxed inside a shielded, sound-proofed chamber with their eyes open.
Results showed that a personal history of depression and a family history of alcoholism had opposite effects on the EEG power spectrum. Teen-age girls with a history of depression, not active depression, showed an enhanced amount of eight to 12 cycles per second brain electrical activity. This is referred to as alpha or slow-wave activity. "In other words," said Bauer, "a subtle abnormality in brain electrical activity is consistently present in these girls, even after the period of acute depression has passed."
A family history of alcoholism was associated with a qualitatively different abnormality in brain function: an enhancement of 19-30 cycles per second. This is referred to as beta or fast-wave activity. A family history of depression did not seem to have an effect on EEG activity, a finding that Adolf Pfefferbaum, director of the Neuropsychiatry Program at SRI International, calls both "interesting" and "intriguing."
"This pattern of association and dissociation suggests potential and different biological markers for liability for alcoholism or depression," he explained. "This possibility for a predictor of alcoholism is strengthened when taken together with another recent publication by Bauer in which he found increased beta power in alcoholics, more so in the men than women."
Another finding of the study was that the effects of a family history of alcoholism occurred in a different region of the brain (left frontal) than the effects of a personal history of depression (right frontal).
"These results suggest that the brain is a very complex organ," said Bauer. "Individuals who possess multiple personal and family risk factors might therefore possess a brain in which multiple areas are affected."
Bauer said the study adds to scientists' growing knowledge base in several areas. "For example," he said, "we found subtle abnormalities in brain function in young girls who have not yet experienced repeated episodes of depression and who have not yet been chronically exposed to antidepressant medication. We also found that a family history of alcoholism is associated with a subtle abnormality in brain function which is different from the abnormality associated with depression."
Although the results of the study have no immediate implications for current treatment, Bauer said that, if replicated, their findings suggest that "treatment for depression might be improved by a thorough assessment of personal history as well as family history.
The presence of both depression and a family history of alcoholism," he said, "might call for a different, or more intensive, treatment strategy than would apply to a depressed patient without a family history of alcoholism."
The co-author of the Alcoholism: Clinical & Experimental Research paper was Victor M. Hesselbrock of the Department of Psychiatry at the University of Connecticut School of Medicine. The study was funded by the National Institute on Alcohol Abuse and Alcoholism and the National Institute on Drug Abuse.