In a study funded in part by the Brain & Behavior Research Foundation, Foundation NARSAD Grantees Charles R. Conway, M.D. and Yvette I. Sheline, M.D., and team found that vagus nerve stimulation (VNS) made positive, long-term changes to the brains of people suffering from major depression. Vagus nerve stimulation works by stimulating the vagus nerve (a nerve that runs from the brainstem to the abdomen) by delivering an electronic pulse for thirty seconds every five minutes. The study included thirteen patients who had major depression over the course of two to twenty years who had not responded to treatment from up to five different antidepressant medications.
Dr. Sheline is well known for her work using brain scans to learn about depression. She conducted breakthrough research in the 1990s using functional magnetic resonance imaging (fMRI) scans to identify structural brain changes in the hippocampus and amygdala in depression that established depression as a brain disease. With a 1998 NARSAD Grant, she went on to use fMRI scans to identify how antidepressants correct abnormal brain function to alleviate symptoms of depression.
In the current study, working with Dr. Conway, study first author and associate professor of psychiatry, Washington University School of Medicine, St. Louis, MO, and team, positron emission tomography (PET) brain imaging scans were used to monitor the treatment’s effects on brain activity in specific regions known to be connected to depression. Each participant had a PET scan before the initiation of VNS stimulation, three months into treatment and at twelve months. After several months, nine study participants experienced reduced depression symptoms and the researchers found that VNS brought about changes in brain metabolism weeks or even months before patients begin to feel better.
“We saw very large changes in brain metabolism occurring far in advance of any improvement in mood,” says Dr. Conway. “It’s almost as if there’s an adaptive process that occurs. First, the brain begins to function differently. Then, the patient’s mood begins to improve.”
Importantly, the researchers also found that VNS affected other deeper structures in the brain, many of which have high concentrations of brain cells that release dopamine, a neurotransmitter that helps control the brain’s reward and pleasure centers and also helps regulate emotional responses. This supports a growing consensus in the field that problems in dopamine pathways may be particularly important in treatment-resistant depression, explains Conway. And he said the finding that vagus nerve stimulators influence those pathways may explain why the therapy can help and why, when it works, its effects are not transient. Patients who respond to VNS tend to get better and stay better.
The study findings were published online on Feb. 15, 2013 in Brain Stimulation.