1. The 'chemical imbalance' theory was a marketing strategy. The drugs were known to affect serotonin; low serotonin was one hypothesis related to depression; the two were married together. On the same basis one could say: I have a toothache; a tot of whisky stops the ache; my toothache is caused by whisky deficiency.
2. It was so successful it was taken as fact, without proof. And repeated as such from doctor to patient. The diabetic/insulin analogy was often used - dreadfully unsuitable. It also managed to ignored the fact that many diabetics manage without insulin.
3. You can only measure brain serotonin on a corpse. Very handy. Blood serotonin levels bear no relation to what's going on in the brain, plus most of the body's serotonin is associated with the digestive system. There is no way of measuring what's going on in someone's brain in terms of serotoninsynaptic junctions.
4. The notion that low serotonin was a cause of depression was one hypothesis (of loads), however it has been largely discounted; including pre-SSRI. "No abnormality of serotonin in depression has ever been demonstrated". If you read the SSRI leaflets carefully, you will note that there is no claim that there is a physical serotonin deficit - it is merely implied by the linking of certain sentences, but the reader is left to add 2+ 2 and through assumption come to the desired conclusion. Rather funnily, in a study that looked for serotonin deficiency, the chemical being measured to look for low serotonin, turned out to be a marker for either low or high serotonin.
5. Other drugs used as anti-depressants have no action upon serotonin.
6. The SSRIs raise serotonin within hours of the first pill - if the 'chemical imbalance' was there, people would be 'cured' of their serotonin deficiency by tea-time.
7. There is no way of measuring this 'chemical imbalance', and most people get standard doses - do we all have the same chemical imbalance, despite disparate age, weight, sex, metabolic differences? I don't think so, makes no scientific sense what-so-ever. Try asking your doctor... "Doctor, I'd like you to measure my imbalance, so we can carefully correlate the dosage to the deficiency, and then take regular repeat measurements so we can scientifically note how the drug is helping me regain the required serotonin level."
8. The SSRIs are mass prescribed - so the chemical imbalance must extend to those treated for ailments like: premature ejaculation, high blood pressure, cysts, cancer, fingernail biting, gambling, standard grief, moving house, being female (hormones make the ladies much more likely to be prescribed), changing job... all of which must be mediated by low serotonin... nope, that holds no scientific water, either.
9. (a) Over time, the action of the drug upon our serotonin receptors doesn't make good reading.
9 (b) What is happening to the dopamine/dopamine system as a result of the increased serotonin, makes equally unedifying bedtime reading.
9 (c) So the drug will cause a neurochemical imbalance within the system and make physical structural alterations, rather than level out some unspecified, unmeasurable deficiency.
10. Depression is often cyclical - it is written (with refs.) that large percentages would get better without intervention - so this 'chemical imbalance' must be therefore be capable of rebalancing itself without the use of an SSRI; this would imply that the SSRIs must also be used in a careful cyclical manner, since a patient with no chemical imbalance at a certain period of time would be at great risk of being chemically over-dosed on serotonin at this inappropriate moment. Nope.. that doesn't sound right, either.
11. The age of Biological Psychiatry stipulates that there is a cause and a drug can cure it. We'll worry about the details later; in the meantime, just believe us, we know what we're doing, and no, we aren't going to release the less than optimal trial details because they might not gel with our P.R.
12. And nope, we'll just gloss over the placebo effect too, because it's a tad disconcerting that this chemical imbalance is rebalanced by placebo to the same extent as our wonderful chemical-rebalancing compound.
13. And, nope, we'll kind of shelve the fact that of the 4 Prozac trials submitted for approval, the 3 which showed some efficacy were the ones where we allowed the secondary medication of anti-anxiety drugs to those who suffered the adverse effects (that's after we thought we'd already weeded out those who were having bad reactions)... since some clever clogs might say that the sedative-type drugs administered were the ones sorting out the 'chemical imbalance', and aiding the depression. And, erm, the one where we didn't administer the anti-anxiety drugs...was the one where there was no statistical difference between the drug and placebo. And, erm, we'd better not say that pre-removing placebo responders to artificially enhance the drug's performance is kind of standard practice, because that casts an even dimmer light on our drug's rebalancing qualities.
14. The chemical imbalance line tells the patient they have a physical problem, that can be addressed by a drug - it implies a straight proven scientific deficiency (untrue)means the patient is less likely to query treatment (true), and more likely take a medication as directed (true)- excellent sales technique. It also moves away from the 'disorder' diagnosis, and implies 'disease'... a massive can of worms, and lots has been written about the less than stellar objectives of this form of presentation. Disease models presented as fact. Highly dubious.
15. The waters get further muddied on the question of measuring the degree of unblinding in the studies, and therefore measuring the validity.
I believed what my doctor told me. Chemical imbalance. Fact. Turns out that my well-meaning physician repeated marketing information, cannily presented as fact, when the 'fact' is anything but. When you research / read up on the non-sponsored literature, and the work deriving from neutral scientific investigation over many years, you suddenly come face-to-face with flat reality. I actually believed that research for drugs had to conform to the kind of scientific principles instilled in trained scientists... neutral observation, avoidance of skew, meticulous collection of all raw data, careful analysis through appropriate use of statistics. What actually goes on, seems to be a sour and sordid manipulation of science, to the detriment of those who will consume the end product.
Of course the SSRIs can produce good responses in some depressed people, but then, as stimulant-like drugs, they should have that effect in everyone who doesn't fall victim to the adverse effect profile... which is why they may be prescribed as a universal cure-all for all sorts of presentations. But, are they curing a chemical imbalance? From what I've read... that would be a big, fat nope. Both to the notion of the imbalance, and to the notion that the drug rebalances the imbalance... curiously by boosting the levels beyond anything the human body experiences under natural physiological conditions i.e. pathologic.
You can take the imbalance research further by looking at what happens to our dopamine levels as a result of the SSRI, and then what that does to the hormones, increased rate of bone loss, eyesight, sexual function... and it does go on a long way... and I haven't, so far, come across valid data which I regard as backing up the 'imbalace' line. Or as it is more correctly termed, the hypothetical imbalance.