No one should believe the chemical imbalance theory

A post on Slate Star Codex argues that the idea that "depression is a drop-dead simple serotonin deficiency was never taken seriously by mainstream psychiatry". There may be some truth in this view, but there's no doubt that many people have been taken in by the theory (see eg. previous post). They're surprised that the theory hasn't been proven. They may even have been told by a psychiatrist that their depression is due to a chemical imbalance.

And there's no doubt that drug companies have taken advantage of these beliefs as shown in the Zoloft (sertraline) advertisement above. True, the commercial does say that the cause of depression is unknown. But it then goes on to suggest that sertraline corrects a chemical imbalance to which depression may be related. And Slate Star Codex doesn't want to totally abandon the idea that "it's very likely it [depression] will involve chemicals in some way".

Actually, the 'chemicals in depression' may not be much different from those that create normal feelings. It may not make much sense to view depression as a neurochemical disorder. The kinds of processes that underlie mental illness at the biochemical level may be no different from those that produce thoughts, feelings and behaviour amongst the 'normal'. We tend to assume that there must be a neuropathological basis for mental illness, as there is a pathological basis for physical illness. But 'mental illness' is very different from physical illness, if only because of the mind-body philosophical problem.

And, the sertraline advert is also misleading in that it says that sertraline "is not habit forming". Antidepressant discontinuation problems do occur with SSRI antidepressants, like sertraline (eg. see previous post). It's not surprising that people may get psychologically dependent on a drug which they think has improved their mood (see my book chapter).