Psychiatric diseases are complicated and variable. The uniqueness of each patient and the situation introduces uncertainties into drug research and into recommendations for patient care. A single biochemical or physiological mechanism will not usually predict the pathological changes or progression of illness for an individual. Both genetic and environmental factors contribute, requiring the various perspectives to explain illness (14, 15). In brain disorders, interacting physical and social systems, behaviors, and personal histories influence data in unpredictable ways (2, 11, 14). As a further complication, drug efficacy and safety data, derived from group responses in CTs, cannot predict drug effects for the individual in clinical care.
