New research published in Molecular Psychiatry examines the “serotonin hypothesis” of depression, which posits that major depressive disorder is caused by a chemical imbalance in the brain that can be treated by regulating serotonin levels. The researchers concluded that the evidence supporting the serotonin hypothesis is not sufficient to establish a strong link between serotonin levels and depression.
Our new review is the first systematic overview of all major areas of research and concludes that there is no evidence of a link between low serotonin and depression https://t.co/fujIfAtD91 THREAD
Dr. Joanna Moncrieff (@joannamoncrieff) 20 July 2022
“Many people are taking antidepressants because they are led to believe their depression has a biochemical cause, but this new research suggests that this belief is not based on evidence,” said lead study author Dr. Joanna Moncrieff, according to the Guardian. “It is always difficult to prove a negative, but I think we can safely say that after a great deal of research over several decades, there is no convincing evidence that depression is caused by an abnormality in serotonin, particularly due to low levels or decreased activity of serotonin.”
The research team examined 17 studies, including 12 systematic reviews and meta-analysis, and found that “there is no consistent evidence for an association between serotonin and depression, and no support for the hypothesis that depression is caused by decreased activity or concentrations of serotonin.”
Evidence has also shown that long-term use of antidepressants may be associated with decreased levels of serotonin. Moncrieff argued that the public should be informed that antidepressants may not be the optimal way to treat depression due to the side effects and withdrawal symptoms associated with the drugs. (Related: New study suggests psychedelic drugs can ‘liberate the minds’ of people with major depression)
Not all experts agree with the result. A spokesperson for the Royal College of Psychiatrists said: “Antidepressants are an effective NICE-recommended treatment for depression and may also be prescribed for a range of physical and mental health conditions.” “We do not recommend anyone to stop taking antidepressants based on this review, and encourage anyone with concerns about their medication to contact their GP.”
Antidepressants are an important component of drug companies, and their use has been on the rise in the United States since 1999, according to Berkeley Politics Journal. NBC News reports that one in six Americans takes some form of antidepressant.
The global market for antidepressants was valued at more than $26 billion in 2020, according to Business Wire.
Even if the serotonin hypothesis is incorrect, this does not mean that antidepressants that target brain chemistry are not an effective way to treat depression, according to Dr Michael Bloomfield, a University College London psychiatrist who was not involved in the research. “Many of us know that taking paracetamol can be good for headaches, and I don’t think anyone would think that headaches are caused by not enough paracetamol in the brain,” he told the Guardian. “The same reasoning applies to depression and medications used to treat depression.”