Melancholy

The precision of medical diagnostic terms is essential to establish the reliability and validity of proposed disease states. While the term “depression” is widely used in society, its meaning varies with the user, an attitude best expressed by Alice in Wonderland's Humpty-Dumpty, “When I use a word, it means just what I choose it to mean – neither more nor less.” In psychology, depression represents a decrease in psychomotor activity or intellectual agility. Within neurophysiology, depression refers to a decrease in the brain's functioning, measured in electrical activity or cerebral blood flow. For the pharmacologist, depression means the decrease in body functions induced by sedatives, soporifics, and anesthetics. In clinical practice, depression describes a normal human emotion, a pathologic state if it is retained too long or too deeply, or a psychopathologic syndrome that may be mild or severe. A clinical depressive episode may be defined by its associated adverse life events or it may strike a subject without cause.