When I did my psychiatry rotation in med school, the most valuable piece of advice I got from one of my attendings was while we were sitting in the conference room, talking about a tragic case of a little boy abused since the age of 5, neglected and physically assaulted, but thankfully no sexual abuse. He still carried horrible emotional scars despite being in a nurturing, safe environment at time of evaluation.
Me and the other medical student sat there flipping through the DSM, trying to pigeon hole this kid into a diagnosis. He lacked 1 criteria for post-traumatic stress disorder. He certainly lacked criteria for major depression. We presented the case to our attending over coffee. He watched us for about 5 minutes before becoming fed up.
"That book can't tell you anything about what your patient has. You're trying to diagnose with DSM, but it can't tell you that someone's depressed. It can't tell you someone is sick. It just tells you what to look for. Is that book going to offer any reassurance? 'You don't have PTSD because you don't have the necessary number of criteria met.' Ridiculous."
He took our DSM's away and asked us what this kid had. And that was when I realized the difference between cookbook medicine and clinical skill. After a certain amount of time, a doc's got to be able to look at someone and say, "You are sick." DSM is the psychiatric diagnostic equivalent of a Brother P Touch. Nice for labeling, but I wouldn't use it for much else.