The present invention is directed to methods and assays for identifying subjects participating in clinical trials that may exhibit a placebo response and identifying treatments for subjects with varying degrees of placebo responses. In one aspect, a method of selecting subjects to participate in a clinical trial is disclosed. In another aspect, methods for treating a subject and determining a treatment dosage are disclosed. In an exemplary embodiment, a method for determining a response to a treatment of a subject having, suspected of having, or at risk for developing a disorder, such as cardiovascular disorder, irritable bowel syndrome, diabetes, autoimmune disorders, inflammation, neurological disorders, chronic pain, cancer, cancer treatments, allergies, depression, migraines, addiction, obesity, and other disorders, syndromes, or diseases, is disclosed.
