There is no clear evidence that depression is caused by low serotonin levels, researchers have said, as they called into question the widespread use of antidepressants.
The new review of existing studies found that the condition is not likely caused by a chemical imbalance and said people should be made aware of other options for treating depression.
However, other experts, including from the Royal College of Psychiatrists (RCP), urged people not to stop taking their medication in light of the findings, and argued that antidepressants are effective.
In the new study, University College London (UCL) researchers said 85% to 90% of the public believes depression is caused by low serotonin or a chemical imbalance.
Most antidepressants are selective serotonin reuptake inhibitors (SSRIs), and were originally said to work by correcting abnormally low serotonin levels.
Lead author Joanna Moncrieff – a professor of psychiatry at UCL – said: “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.”
The review looked at studies involving tens of thousands of people. One of the findings was that research that compared levels of serotonin and its breakdown products in the blood or brain fluids did not find a difference between people diagnosed with depression and healthy people.
The authors also looked at studies where serotonin levels were artificially lowered in hundreds of people and concluded that lowering serotonin in this way did not produce depression in hundreds of healthy volunteers.