Saint Louis University, working in collaboration with Washington University School of Medicine, conducted a pilot study of brain scans of a small group of depressed patients who received vagal nerve stimulation after failing other therapies.

Positron emission tomography (PET) scans showed significant changes in brain activity starting three months after vagal nerve stimulation treatment began. These changes continued to evolve over the course of the next 21 months. These changes in brain scans appear to “roughly parallel” the significantly delayed effects that psychiatrists observed in improvement in mood.

“The effects come after a significant period of treatment time,” said Charles Conway, M.D., an assistant professor of psychiatry at Saint Louis University School of Medicine and the lead investigator. Psychiatrists are not used to such a long time lag before a treatment begins to be effective, he added.

Conway cautioned the findings are preliminary and need replication. “But they suggest that in this type of therapy, the brain takes a relatively long time to change, perhaps as long as a year or more. In this sense, vagal nerve stimulation may represent a paradigm shift in the way we view depression treatment. Patients may have to be instructed to ‘be patient,’ with the expectations that the antidepressant effects will be slow to come.”

Conway examined the brain scans of patients at three, six, twelve and 24 months intervals after they began receiving vagal nerve stimulation. Eight patients participated in the study for the three and six month scans, six patients at twelve months and four patients at 24 months. The size of the study group grew smaller during the two year investigation.; Source: Saint Louis University