Hello Fuzzy,

I would say that depression is an 'illness' as meaning 'diminished function' because of what I've read. I've a book called 'Mapping the Mind' by Rita Carter (and it's really interesting), and in that she says that the brain of a depressed person behaves differently to the brain of a non-depressed person. In depressed people, parts of the brain were found to be underactive, such as the parts which creates self-willed actions, and a part which controls attention and interest in external affairs which suggests, she says, why depressed people tend to be pretty self-absorbed. The brain's 'emotional control centre', as she describes it, is also underactive. And another scientist reckons that over-active parts of the brain keep in place a sequence of events which ensure the continuation of depression. It isn't explained why depression gets better though ...