Almost two years old now, but just now seen by me, a review of Jonathan Sadowsky's Empire of Depression, plus some good general discussion of the complexities, by the always-valuable theodore Dalrymple. He generally approves of Sadowsky's thinking, but finds there are omissions.
The author does not (in my opinion) sufficiently consider the cultural significance of the replacement of the word unhappiness by depression in common parlance. The practical effect is considerable. An unhappy person must either put up with his unhappiness, or analyse the reasons for it and try to change either himself or his circumstances. The depressed person is declaring himself ill and placing the responsibility on someone else to cure him. In present medical circumstances, in which doctors have very little time for each patient (and much of that taken up with entering data, or pseudo-data, on a computer), a prescription is the most likely outcome.