For many people with depression, pharmacological treatment is a sufficient course of action. However, there are some people who do not respond to the standard battery of antidepressant treatments. In order to treat this population, researchers at Washington University School of Medicine in St. Louis began doing research involving a brain implant and scans of people with treatment-resistant depression.

The study, which will be published in Brain Stimulation, followed 13 individuals with treatment-resistant depression. The people in the study had varying experiences with depression: some had been diagnosed for more than 20 years, although the average length of depressive experience was at least two years. They had all been on various antidepressant medications and some had tried as many as five different types.

In order to participate in the research, participants had surgery to have a device inserted into their brains. The device was positioned such that it could electronically stimulate the left Vagus Nerve. The device was set to deliver a 30-second electronic stimulus to the Vagus Nerve every five minutes.

Notably, the Vagus Nerve, which is part of the parasympathetic system, plays a major role in emotional regulation, homeostasis, and dealing with stress.

The researchers performed brain scans of the participants before beginning the Vagus Nerve stimulation, and again three and 12 months after beginning the treatment. Nine of the 13 subjects eventually experienced improvement in their depression.

Of the participants whose brains responded, the scans found significant changes in brain metabolism after just three months of stimulation. These changes were typically followed by improvements in the symptoms of depression. Although how this treatment works to improve depression is not completely understood, Charles Conway, MD., the study’s first author states that, “We saw very large changes in brain metabolism occurring far in advance of any improvement in mood. It’s almost as if there’s an adaptive process that occurs.”

Additionally, the Vagus Nerve, which is one of the longest nerves in the body, has a branch that connects it to the ear and which may possibly be activated by sound stimulation. The improvements experienced by those using the iLs air/bone conduction headphones (and iLs Pillow)  indicate that this method of delivering sound might be stimulating the Vagus Nerve, and thus the Parasympathetic Nervous System as a whole. iLs is currently launching research to determine if this indeed is the case.