Psychology IS mental illness, is that what you mean?
LOL -
Actually there are psychologists who have been inducted into AAAS and the American Academy of Arts and Sciences. They’ve never seen patients or dealt with mental illness. They’re not practitioners.
Academic/scientific psychology deals with such diverse topics as math models, neuroimaging, cognitive functioning, decision making. In fact a couple of them won Nobels - but in economics because there is no prize in psychology. (None in math either.)