A new study has shown that that the brain's serotonin system differs between men and women, leading researchers to state that this might be the reason why depression and chronic anxiety are more common in the fairer sex.
Serotonin is a brain neurotransmitter that is critical to the development and treatment of depression and chronic anxiety, conditions that, for reasons still unknown, are much more common in women than in men.
The research group at Karolinska Institutet has now shown using a PET (Positron Emission Tomography) scanner that women and men differ in terms of the number of binding sites for serotonin in certain parts of the brain.
The findings reveal that women have a greater number of the most common serotonin receptors than men. They also show that women have lower levels of the protein that transports serotonin back into the nerve cells that secrete it. It is this protein that the most common antidepressants (SSRIs) block.
"We don't know exactly what this means, but the results can help us understand why the occurrence of depression differs between the sexes and why men and women sometimes respond differently to treatment with antidepressant drugs," said lead author of the study and associate professor Anna-Lena Nordstrom.
The group has also shown that the serotonin system in healthy women differs from that in women with serious premenstrual mental symptoms.
These results suggest that the serotonin system in such women does not respond as flexibly to the hormone swings of the menstrual cycle as that in symptom-free women.
"These findings indicate that when developing antidepressants and anti-anxiety drugs, scientists should evaluate their effect on men and women separately, as well as their effects before and after menopause," said Nordstrom.
The study is to be presented in a doctoral thesis by Hristina Jovanovic at the end of February.