Joanna Moncrieff and colleagues recently published a systematic umbrella review of evidence for depression being caused by either lowered levels or activity of serotonin. They reviewed 17 previous studies which had investigated serotonin and metabolite levels in body fluids, serotonin receptors in depressed patients vs those without depression, the serotonin transporter, the serotonin gene as well as studies looking at tryptophan depletion (this lowers available serotonin).

They did not find convincing evidence from these areas of study that depression is caused by either lowered serotonin levels or activity. It will be interesting to see the discussion that ensues around the biochemical basis of depression.

Read the full piece on the Nature website.