Bad Science has a fantastic article on antidepressants and the widely-promoted but scientifically unsupported ‘low serotonin theory’ of depression.
Owing to a huge advertising push by drug companies, not only the ‘man on the street’, but also a surprisingly large numbers of mental health professionals (clinical psychologists, I’m look at you) believe that depression is linked to ‘low serotonin’ in the brain.
The only drawback to this neat sounding theory is that it is almost completely unsupported by empirical evidence or scientific studies.
Experiments that have deliberately lowered serotonin levels in the brain have found that it is possible to induce ‘negative mood states’ (usually milder and as short-lasting as a slight hangover), but these do not even begin to compare to the depths of clinical depression.
In terms of patients with the clinical mood disorder itself, not a single study has found a link to reduced serotonin.
Bad Science neatly reviews the science, and also discusses a new research study which chased up journalists that propagated the myth to ask for their sources.
Needless to say, none of them had any sound scientific basis for their claims.
This is not to say that antidepressants don’t help treat depression, (evidence suggests they do – although the effect is more modest than drug companies would have us believe), or that neurobiology isn’t important (by definition, if it’s a change in thought and mood, it’s a change in brain function).
If you’re interested in the history of how the ‘low serotonin hypothesis’ came to be thought up and then subsequently promoted, despite the lack of evidence, Professional Psychology: Research and Practice recently published a great article on the topic [pdf].