When it comes to contemplating the legitimacy of mental illness, it is the 'mental' aspect of the term that I think really throws people for a loop, with its entailment of a complex interface between biological and psychosocial factors. Thomas Szasz may have been right to propose that 'brain disease' would make a more appropriate, and less misleading term.
Unlike a lot of people in today's society, I will happily admit to taking anti-depressants. A mental illness is just that - an illness, which needs treating. If I had a physical ailment I wouldn't think twice about taking the medication, so I don't understand why there is such a taboo on medication for mental illnesses.
Winston Churchill called it the 'Black Dog'. Every year, thousands of people in Britain die because of it. One in three people will suffer from it at some point in their life. Why, then, are we so afraid to talk about depression? The problem is particularly striking amongst my own demographic, young men under the age of thirty.