Studies of postmortem brains of patients diagnosed with major depressive disorder (MDD) showed a 31 percent greater than average number of nerve cells in the portion of the thalamus involved with emotional regulation. Researchers also discovered that this portion of the thalamus is physically larger than normal in people with MDD. Located in the center of the brain, the thalamus is involved with many different brain functions, including relaying information from other parts of the brain to the cerebral cortex.
The findings, published in today's issue of The American Journal of Psychiatry, are the first to directly link a psychiatric disorder with an increase in total regional nerve cells, said Dr. Dwight German, professor of psychiatry at UT Southwestern.
"This supports the hypothesis that structural abnormalities in the brain are responsible for depression," he said. "Often people don't understand why mentally ill people behave in odd ways. They may think they have a weak will or were brought up in some unusual way.
"But if their brains are different, they're going to behave differently. Depression is an emotional disorder. So it makes sense that the part of the brain that is involved in emotional regulation is physically different."
Four groups were represented in the study: subjects with major depression, with bipolar disorder and with schizophrenia, as well as a comparison group with no history of mental illness. Major depression is characterized by a depressed mood and lack of interest or pleasure in normal activities for a prolonged period of time, while bipolar disease is distinguished by alternating periods of extreme mania or elevated mood swings, and severe depression. Schizophrenia often results in psychotic episodes of hallucinations
Contact: Donna Steph Hansard
UT Southwestern Medical Center