Permanent sadness, hypersomnia, bulimia. Seasonal depression returns with fall. Researchers have finally understood its origin in the brain.
She makes her comeback every fall. Seasonal depression, or seasonal affective disorder, is associated with lack of light. Danish researchers have understood the mechanism at work in the brain. The results of their work were presented at the Congress of the European College of Neuropsychopharmacology (ESC) in Berlin (Germany).
Finding the “button” in the brain
The “winter blues” affects up to one in six people in northern European countries. There are fewer of us in France, but this mental disorder remains a scourge for some. Because at the end of each year, it’s the same story: permanent sadness, irritability, hypersomnia and bulimia. Seasonal depression is well known, its mechanism was less so.
“We think we have found the button that the brain turns on when it has to adjust serotonin to seasonal changes,” summarizes Brenda Mc Mahon, who led the research. In seasonal affective disorder as in classic depression, it is indeed serotonin that is involved. It is more precisely how the body regulates this neurotransmitter, which affects mood, that is disturbed.
Light therapy and antidepressants
Dr Mc Mahon’s team examined 11 patients with seasonal depression and 23 healthy patients using PET scans, carried out in summer and winter. Members of the first group had on average 5% higher levels of serotonin transporters than the others.
“The serotonin transporter (SERT) carries serotonin to nerve cells where it is not active; therefore the more the SERT is active, the less the serotonin is, ”summarizes Brenda Mc Mahon. “Daylight keeps these parameters relatively low. But as the nights get longer during fall, SERT levels rise, causing active serotonin levels to drop. “
These findings serve above all as confirmation, because the treatments target serotonin: they consist in prescribing antidepressants, performing psychotherapy and especially light therapy.
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