Saturday, November 28, 2015

Simplistic notion of antidepressants correcting chemical imbalance in the brain is publically untenable

Jeffrey Lacasse and Jonathan Leo have published an update (see new article) on their article from 10 years ago on drug company advertisements about antidepressants correcting serotonin levels in the brain. As they say, "Some advertisements were more tentative or clever in their wording than others, but it seemed obvious that the drug companies were at least pushing the boundaries" of the scientific evidence. What they've found from data collected in 2014/5 is that the simplistic narrative of chemical imbalance is no longer widespread. Drugs tend to be advertised as "affecting" neurotransmitters rather than normalising transmitter levels. There are still problematic advertisements but the language has been moderated substantially.

I don't think we should necessarily be taken in by this change. Although simplistic notions of biochemical imbalance may no longer be publically tenable or displayed in advertisements, I'm not sure if practising psychiatrists really care that the theory is wrong. In fact, they probably still think that antidepressants correct a chemical imbalance, even if it hasn't definitely been shown in research (eg. see previous post). They like to think antidepressants work in practice, so there must be some reason why they work. So, even if the academic evidence isn't there for 'chemical imbalance', psychiatrists still function as though it justifies their clinical practice. In fact, they may still indicate this to patients. Few psychiatrists tell patients that even in the clinical trials the difference between placebo and active treatment is small. Any difference was called 'clinically insignificant', at least as regards reducing depressive symptoms, by NICE in a previous version of its depression guideline (see my BMJ eletter). There are also a substantial number of patients that do not improve in the clinical trials. Antidepressants are not always as effective as psychiatrists may make out to patients.

Psychiatrists use the chemical imbalance theory as a means of persuading patients to take their medication (see another eletter). The role of psychiatry is to give hope to depressed people. It is also to be honest with them about the cause of their problems and the appropriate treatment. Patients are able to understand that the 'chemical imbalance theory' has only ever been a theory. What they find more difficult to appreciate is why they are told that this theory has been proven, when this is clearly not the case.

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