Consider this segment of a debate between Thomas Szasz and several other academics concerning depression as a mental illness:
GOODWIN: As you yourself said, we don’t involuntarily treat people for medical diseases. I’d like to as you . . . do you think Alzheimer’s is a disease?
SZASZ: Of course it is a disease.
GOODWIN: And it involves behavior?
SZASZ: Of course it involves behavior. Doesn’t having a cold involve behavior?
GOODWIN: You said if it involves behavior it couldn’t be a disease.
SZASZ: No, you don’t diagnose it, Alzheimer’s, if I may remind you. Who discovered Alzheimer’s? A pathologist, on the corpse.
GOODWIN: Now they are close to diagnosing with brain imaging . . .
SZASZ: Brain imaging is a great scientific discovery.
GOODWIN: Now they do that with depression as well, you are aware of that?
SZASZ: Of course I am aware of that.
GOODWIN: So here you have two illnesses, one we call Alzheimer’s which you say is a disease, it involves a whole range of behaviors, feelings, thinking, behaviors. There’s another one that involves behavior, feelings, thinking, behaviors . . .
SZASZ: But depression is a highly reversible phenomenon.
GOODWIN: Is that your criterion for disease? What about pneumonia?
SZASZ: No, but Alzheimer’s is not.
GOODWIN: Does that mean diseases are not reversible?
SZASZ: Look, the criterion for disease is not made by you and me. As you know, depression is not listed in textbooks of pathology. Maybe when it’s listed in textbooks of pathology I might be willing to concede, like Dr. Klein suggests, that it’s like neuro-syphilis or epilepsy, the history of medicine, it’s quite correct, you discover new diseases, like AIDS.
Why would Szasz classify Alzheimer’s as a disease, and not depression, given the apparent involuntary physiological effects (lower serrotonin levels, brain scan differences) that are present in both conditions?
The full debate is here:
EDIT: Clarified some points, improved my question.