Many antidepressants might not be treating the condition, because they are being used to correct a cause of depression that does not actually exist, new research has suggested.
A new review of existing studies concludes that the “chemical imbalance” theory of depression, in particular low levels of serotonin, does not stand up to scrutiny.
Serotonin is a chemical transmitter that appears to play a role in governing mood and emotions.
Most antidepressants are selective serotonin reuptake inhibitors (SSRIs), and were originally said to work by correcting abnormally low serotonin levels.
However the umbrella study, carried out by researchers at University College London (UCL) and published in Molecular Psychiatry, suggests that depression is not likely caused by a chemical imbalance, and calls into question what antidepressants do.
The number of people in England taking antidepressants has been rising, according to NHS figures, with 8.3 million patients receiving them in 2021/22, a 6% rise on the previous year when the figure was 7.9 million.
The UCL team said 85% to 90% of the public believes that depression is caused by low serotonin or a chemical imbalance, however this does not appear to be the case and patients should be made aware of other options for treating depression.
The lead author of the review, Joanna Moncrieff, professor of psychiatry at UCL, said: “It is always difficult to prove a negative, but I think we can safely say that after a vast amount of research conducted over several decades, there is no convincing evidence that depression is caused by serotonin abnormalities, particularly by lower levels or reduced activity of serotonin.
“The popularity of the ‘chemical imbalance’ theory of depression has coincided with a huge increase in the use of antidepressants…
“Thousands of people suffer from side-effects of antidepressants, including the severe withdrawal effects that can occur when people try to stop them, yet prescription rates continue to rise.
“We believe this situation has been driven partly by the false belief that depression is due to a chemical imbalance.
“It is high time to inform the public that this belief is not grounded in science.”
However the Royal College of Psychiatrists said patients should continue to take the medication they had been prescribed.
A spokesman said: “Medication should be available for anyone who needs it. We would not recommend for anyone to stop taking their antidepressants based on this review, and encourage anyone with concerns about their medication to contact their GP.”
Professor Allan Young, director of the Centre for Affective Disorders at the Institute of Psychiatry, said of the new study: “The (undiscussed) elephant in the room is the good evidence of the efficacy and acceptability of serotonergic antidepressants.
“The use of these medicines is based on clinical trial evidence which informs their use for patients.
“This review does not change that.”