11% of the population is on some type of antidepressant. Many on antidepressants are on them for years or life. However, as a functional health care provider, we know that 95% of the bodyâ€™s serotonin is housed in the gut, not the brain. So if depression is a lack of serotonin, the first place you should look is the gut! Fixing the balance within the gut and decreasing inflammation have shown positive results in regards to depression.