SSRIs have long been controversial because they reflect a theory of depression causation that is a longstanding source of debate. While the chemical imbalance theory has been largely superseded, serotonin levels may still play a role in increasing a person’s risk for depression. Low serotonin levels have been linked to increased inflammation. High levels of inflammatory biomarkers are commonly found in depressed patients, suggestion a relationship between serotonin, inflammation, and depressive symptoms, even if the exact details remain unclear.