Aug. 6, 2004 — Depressed people have overactive brain circuitry, a new study shows.

It’s more evidence that vulnerability to clinical depression is an inherited trait — and that patients need to continue their treatment, including medications, even after depression fades, writes researcher Alexander Neumeister, MD, with the mood and anxiety disorders program at the National Institutes of Mental Health. Treatment with antidepressants is recommended for six to nine months — or longer — to help prevent a recurrence of depression.

His paper appears in the latest issue of the Archives of General Psychiatry.

In their study, Neumeister and his colleagues looked at the relationship between the emotion-regulating chemical serotonin and major depressive disorder. Numerous studies have linked lower levels of serotonin in the brain with clinical depression and suicide.

But is this serotonin deficiency part of a genetic predisposition to clinical depression? Or is it something that occurs over time, creating the depression? That’s what this group of researchers examined.

The 27 patients in the study all had serious depression that was in remission and was not being treated with medication. Some patients were given an “active cocktail” that temporarily reduced levels of the brain chemical tryptophan, which is transformed into serotonin in the brain. Some patients received a placebo cocktail.

Then each volunteer had a brain scan. A radioactive tracer in the cocktail revealed where the brain was more active.

The majority of volunteers taking the active cocktail — 59% — had a temporary return of depression symptoms; their mood lifted to normal the next day, reports Neumeister. None of those receiving the placebo cocktail had a recurrence of depression symptoms.

These patients showed increased brain activity in the front and center of the brain, areas involved in regulating emotions and motivation. These areas have been implicated as centers of depression, he explains.

While other researchers have considered this increased activity to be temporary, this new evidence shows that this overactive brain circuitry is likely an underlying vulnerability trait for clinical depression, Neumeister writes.

SOURCE: Neumeister, A. Archives of General Psychiatry, August 2004; vol 61: pp 765-773.