orpheus wrote:But maybe I'm mistaken. Aren't neurotransmitters chemicals?

The problem isn't that the term "chemical imbalance" is incorrect, but rather the opposite: it is technically correct. However, it is so correct that it is meaningless. In other words, all it is saying is, "The brain is doing stuff". And of course the brain is doing stuff because the brain controls our behaviors and we're describing a problem with our behaviors. So it explains everything, and something that explains everything explains nothing.

For example, what causes addiction? A chemical imbalance. What causes schizophrenia? A chemical imbalance. What causes anger? A chemical imbalance. What causes you to choose cereal over toast in the morning? A chemical imbalance. It doesn't tell us anything and it would almost be more useful to say, "The brain did it". What causes depression? "Stuff in the brain".

Another problem is that the term can be misleading. The finding that antidepressants can be helpful doesn't tell us anything about chemicals in the brain, yet we instinctively want to use it as evidence that there is a biological brain problem with depression. The comparable situation would be to suppose your dog dies and you get a bit sad, and someone gives you some ecstasy. Suddenly you aren't sad any more, but it would be unhelpful to suggest that your sadness was caused by a "chemical imbalance". In a sense, it is a chemical imbalance because the processing of thoughts and emotions is the unbalancing of chemicals in the brain, but we all know that the sadness was caused by the death of the dog. (Note: I'm not trying to say that depression is like "being sad", nor that antidepressants work exactly like ecstasy, instead it's just an analogy of the flaw in simplistic reasoning).

Although on a slightly different topic, I think the issue is dealt with quite well by Neuroskeptic's post here: Brain Scan Proves that the Brain Does Stuff.

Gallstones wrote:Samsa, you are so relative about everything that going by you nothing means anything.

Hmm.. I can be a difficult bastard at times ( ), but I think on this issue I'm not being relative at all. If people were to say "depression is caused by a lack of X in the brain" or "depression is caused by a combination of these psychosocial variables" then that would be meaningful - it would be testable, measurable, and (importantly) falsifiable. But statements like "It's a chemical imbalance" literally describe every single thought, belief, and behavior of a person. It's like trying to describe a mechanical fault in a car by saying it's caused by "some kind of movement within the engine".

Grace wrote:orpheus wrote: "Grace, I'm sorry, but I have no idea what you're saying here."

I'm sorry you threw away your product information sheet without reading it.

But even assuming this is true, it's irrelevant to whether the drug works or not. We didn't know how aspirin worked until relatively recently, and we still don't know how some antimalarial drugs work - but if I get malaria, I'm going to go with whatever treatment has been shown to have the best effect with limited side effects. Whether they know how it's working would be of no concern to me. Essentially, if we rejected a treatment simply because we don't know the exact causal mechanism, then we'd have to reject a lot of mainstream (and lifesaving) medicine.

I suspect the reason why there are many theories explaining how antidepressants could work is simply because there are many causes of depression, so it will probably be difficult to determine one single causal mechanism since there is more than one way in which they could produce a beneficial effect. We know what antidepressants do to the brain, it's just understanding the interaction between that and depression which is still under investigation.

Also, information sheets for drugs aren't the best source of scientific information. Most of the "side-effects" listed on drugs cannot be demonstrated to be caused by the drugs, and are likely to be coincidental symptoms entirely unrelated to the drug. However, due to the early warning system that medicine has and the legal issues surrounding pharmaceutical companies, they are forced to list any possible side-effects, even if there is absolutely no evidence to suggest that their drugs could cause those symptoms.