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Vagus gadgets have mixed evidence
Implanted stimulators
Implanted vagus nerve stimulators are placed under the skin of the chest by surgery and stimulate the left vagus nerve. They are FDA-approved for treatment resistant depression and some epilepsy, though in some studies they didn't work that well for those conditions.
Devices sold for the neck
The ones sold online go over the neck. In one study, people did stressful things like solving annoying math problems, and zapping their necks with the device seemed to lower their stress afterward. Other studies point to possible help for PTSD and cluster headaches.
Who pays for the research
In the conflict of interest sections of several of those papers, the researchers are getting funding from the companies that make the devices. A free way to engage the same nerves has more evidence behind it: slow breathing.
How does stimulating a nerve treat depression?
Electrical pulses sent up the vagus nerve reach a relay in the brainstem called the nucleus tractus solitarius, which connects to regions that regulate mood, sleep, and arousal. Researchers do not fully understand which of these pathways produce the benefit. The US Food and Drug Administration approved vagus nerve stimulation for epilepsy in 1997 and for treatment-resistant depression in 2005. It was the first brain stimulation treatment of its kind approved for depression.
Why do devices target the left vagus nerve?
The right vagus nerve sends more fibers to the heart's natural pacemaker, which sets the heartbeat. Stimulating the right side therefore carries a greater risk of slowing the heart. The left vagus nerve has fewer of those cardiac fibers, so clinicians chose it for implanted stimulators. This difference between the two sides was established in animal studies before the first implants.
Why do funding sources matter in studies?
Industry sponsorship has been linked to rosier results across research on drugs and medical devices. A 2017 Cochrane review led by Andreas Lundh analyzed dozens of comparisons and found that industry-sponsored studies reported more favorable efficacy results than independently funded ones. Journals now require authors to disclose funding and conflicts of interest in each paper. The disclosure section is where readers can see who paid for the work.
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