The hypothesis that depression is related to serotonin has been debated for more than 60 years, and new research by psychiatrists at Imperial College London and King’s College London shows that depressed patients have a reduced serotonin response. This is the first direct evidence of diminished serotonin release in the brains of depressive patients, according to a study published in the journal Biological Psychiatry.
The study involved 17 patients with Parkinson’s disease-related major depression or depression and 20 healthy volunteers.
Participants underwent PET scans, which use radiotracers to reveal how much serotonin is bound to certain receptors in the brain.
Participants were given a dose of amphetamine, which stimulates serotonin release, and scanned again, and the researchers found that those with depression had a reduced serotonin response.
Study co-author Oliver Howes, a psychiatrist at Imperial College London and King’s College, said it was the first direct evidence of reduced serotonin release in the brains of people with depression.
The hypothesis that depression is related to serotonin may also explain why the commonly used antidepressants “selective serotonin recovery inhibitors” are effective.
The serotonin hypothesis stems from evidence from postmortem brain and blood samples suggesting that serotonin deficiency may be associated with depression.
Because the main class of antidepressant drugs, selective serotonin reuptake inhibitors (SSRIs), effectively provide a plausible biological mechanism, which is why serotonin in the brain is called the “happy hormone.”
The Results will improve new treatments
There is currently no conclusive evidence that serotonin abnormalities are the underlying cause of depression, but addressing this issue is critical to providing better treatments.
The latest paper adds to the idea that serotonin plays a role and shows a new brain imaging technique that could lead to a better understanding of why SSRI drugs fail to pave the way for 10 to 30 percent of patients.
Catherine, a professor at Oxford University who was not involved in the work, described it as an important discovery as scientists found evidence of reduced serotonin release.
While few in the field would argue that all depression is the result of low serotonin, the findings “are very consistent with the idea that serotonin may play an important role”.
What is Serotonin?
Serotonin, 5-hydroxytryptamine, is a hormone and a neurotransmitter. It is therefore a substance that acts to transmit information between neurons. It is located in the central nervous system, the cardiovascular system, the intestinal nervous system and the blood. Serotonin is quite complex, and has many functions in our body, this is due to its receptors, to which serotonin is connected.