Functional Medicine is a systems biology–based approach that focuses on identifying and addressing the root cause of disease. Each symptom or differential diagnosis may be one of many contributing to an individual’s illness. A diagnosis can be the result of more than one cause. For example, depression can be caused by many different factors, including inflammation. Likewise, a cause such as inflammation may lead to a number of different diagnoses, including depression. The precise manifestation of each cause depends on the individual’s genes, environment, and lifestyle, and only treatments that address the right cause will have lasting benefit beyond symptom suppression.