In this 2 1/2-minute segment from a PBS Special, Dr. Mark Hyman says diseases are names that “tells us nothing about the real reason or causes for them.” According to Dr. Hyman, the root of disease are a result of 7 core biological systems being out of balance. To learn more about the 7 key systems in your body and the imbalances that lead to illness, see “Dr. Hyman’s UltraMind PBS Special.