While the results of these studies are promising, researchers are still trying to figure out exactly how Botox treats depression.
Initially, they thought the antidepressant effects of Botox might be related to improved appearance. Having fewer wrinkles, they hypothesized, might improve someone’s mood.
However, a 2016 review of the earlier studies found that the severity of a person’s frown lines didn’t impact their results. For example, people with very few frown lines still reported similar results. This suggests that improved appearance isn’t a factor.
A more likely explanation of the benefits of Botox for depression has to do with a “facial feedback” mechanism. Facial expressions send certain feedback to the brain. Emotions like fear, sadness, or anger can result in the contraction of muscles in the forehead that causes the glabellar frown lines.
In people who are depressed, the activity of the muscles that cause these frowns is increased. Blocking these frowning muscles with Botox may result in improved moo