That's from a depressed Dalrymple:
For every person who says “I’m unhappy” there must now be a thousand who say “I’m depressed.” The change in semantics is important: the person who says he is unhappy knows that there is something wrong with his life that he should try to alter if he can; whereas the person who says “I’m depressed” is ill, and it is therefore the responsibility of someone else — the doctor — to make him better.
For the sorts of Psychiatrists who find it valuable to probe below the surface, there are many sorts of depression and many causes. Even grief can sometimes lead to a debilitating depression.
In my private office, the most common "cause" of agonizing, if not always debilitating, depression is narcissistic injury. These patients often can benefit enormously by psychotherapy alone, and can end up far healthier and stronger than before.
I posted on the topic of Studying Happiness earlier this week.