New Depression Therapy Can Take Months to Work

It takes time - between three and 12 months - before a new type of therapy for treatment-resistant depression starts to benefit patients, according to new preliminary brain scan research that confirms earlier observations by psychiatrists about vagal nerve stimulation.

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 of a vagal nerve stimulation research project conducted between 2000 and 2004.

Psychiatrists are not used to such a long time lag before a treatment begins to be effective, he added.

"This is very different from the delays we see with existing treatments for depression, including pharmacotherapy and electroconvulsive therapy (ECT)," Dr. Conway said. "The biggest changes in the brain that we're noting occur between 12 and 24 months after patients began receiving vagal nerve stimulation. In psychiatry, we're used to seeing results after six to 12 weeks."

Dr. 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."

The good news, however, seems to be that those who benefit from the treatment stay better.

"The existing evidence suggests that about 70 percent of patients who get better from vagal nerve stimulation at one year, stay better at two years," Dr. Conway said. "That is unheard of in a depressed population this severe, and suggests that the brain changes induced by this treatment appear to be long-lasting."

Dr. Conway examined the brain scans of patients at three, six, 12 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 12 months and four patients at 24 months. The size of the study group grew smaller during the two year investigation.