Antidepressants questioned: No ‘clear evidence’ depression caused by low serotonin levels, review says

A doctor holds a stethoscope (Lynne Cameron/PA) (PA Archive)
A doctor holds a stethoscope (Lynne Cameron/PA) (PA Archive)

Academics are questioning the widespread use of antidepressants, claiming there is “no convincing evidence” that depression is caused by low serotonin levels.

Authors of the review published in Molecular Psychiatry claim the chemical imbalance theory of depression is “wrongly being put forward by some professionals and the public widely believes it”.

Lead author Joanna Moncrieff said “we do not understand what antidepressants are doing to the brain exactly” and warned against giving patients “misinformation”.

A co-author and training psychiatrist, Dr Mark Horowitz, said he had been taught that depression was caused by low serotonin and he had also taught this to his students.

“Being involved in this research was eye-opening and feels like everything I thought I knew has been flipped upside down.”

The review is an overview of existing research and studies published over decades and involving tens of thousands of participants.

“We can safely say that after vast amounts of research….there is no convincing evidence that depression is caused by serotonin abnormalities, particularly by lower levels or reduced activity of serotonin,” Ms Moncrieff said.

The increasing prescribing of antidepressants has been called into question as a result.

Ms Moncrieff said one in six adults in England and two per cent of teenagers are being prescribed an antidepressant in a given year.

“Many people take antidepressants because they have been led to believe their depression has a biochemical cause, but this new research suggests this belief is not grounded in evidence,” she said.

Research comparing levels of serotonin and its breakdown in blood or brain fluids did not find a difference between people with depression and “healthy control” participants, the paper said.

Around one in five adults experienced some form of depression in early 2021, the Office for National Statistics said.

This is an increase since November 2020 and more than double that observed before the Covid-19 pandemic.