In accordance with the AMA Guides to the Evaluation of Permanent Impairment (AMA Guides), Chapter 18, Pain, pain that is attributable to mental illness does not also qualify for an additional pain-related evaluation. Evaluators must discriminate between presentations of pain that represent mental illness vs those that do not and must decide whether to rate using Chapter 18 or 14. Dichotomous thinking often opposes the notion of psychological vs physiological-organic presentations, but all presentations of pain include psychological aspects, and all mental illnesses include physiological aspects. One type of illustrative mental illness involves conditions that are overtly mental but have been found via extensive scientific study to have a physiological basis (eg, schizophrenia and Alzheimer's disease). Another presentation that is claimed to be of a medical nature actually overlaps with psychological issues (eg, complex regional pain syndrome, type 1 [CRPS-1] and fibromyalgia). Further, the AMA Guides summarizes the lack of a strong correlation between tissue damage or physiology and pain: Pain can exist without tissue damage, and tissue damage can exist without pain. Pain, chronic pain, and impairment from pain are largely, even primarily, psychological phenomena. Accordingly, the determination whether to rely on the pain chapter or the mental/behavioral chapter in the evaluation of a pain presentation cannot be reduced to a misleading dichotomy of psychological vs organic pain.