Study finds first evidence of link between low serotonin levels and depression

Scientists claim to have found the first proof that people with depression have a reduced capacity for releasing a brain chemical.

An influential review published in July that found "no clear evidence" that low serotonin levels are responsible for depression, was challenged by findings from a brain-imaging study. Scientists at Imperial College London found that people with depression have a decrease in the brain chemical serotonin.

Prof Oliver Howes, a consultant psychiatrist based at Imperial College and King's College London, is a co-author of the study. The question has been debated for 60 years, but all of the indirect measures have been used. This is a crucial step.

Evidence from brain and blood samples suggested that there was a deficit in the brain chemical serotonin. The brain chemical is sometimes referred to as a "happy hormone" due to the fact that the main class of antidepressants are effective.

Resolving the question of the underlying cause of depression is important to provide better treatments. The paper shows a new brain scanning technique that could lead to a better understanding of why some patients don't respond to certain drugs.

It is the closest anyone has been to this point. It is difficult to measure these transmitters in the brain of a living person. We can't use a pipette to take a sample. We are likely to come this close.

Seventeen patients with major depression or depression linked to Parkinson's disease were part of the study. The participants were given a Positron Emission Tomography Scan that showed how much serotonin was binding to the brain. They were scanned again after receiving a dose of amphetamine, which stimulates the release of a brain chemical. The researchers found that the patients were depressed.

The University of Oxford's Prof Catherine Harmer was not involved in the work. She said that it was noteworthy that they found evidence for a lower release of the brain chemical. The findings of the study were very much in line with the idea that serotonin may play an important role in the development of depression.

Others weren't sure if it was true. The results were questioned by Eiko Fried. The conclusions drawn by the authors are not in line with the evidence presented. The statistical analyses do not support the theory of depression.

The professor of Psychiatry at University College London who led the review that concluded there is no evidence that chemical imbalances in the brain cause depression said the latest paper won't change her mind. She pointed to the size of the study and the fact that it still looked like a weakness. She said that the study didn't provide convincing evidence that a serotonin abnormality is the cause of depression.

Howes said that the findings would need to be replicated and that further studies would need to be done to determine if there is a link between the two conditions. Current treatments don't work for everyone and that's why it's important Some people can't find any treatment that will help them because the first treatment doesn't work.