According to the authors of a study reported in Science Daily:
A new study being published in the September 15th issue of Biological Psychiatry now reports on important sex and genetic differences in the way that men and women react to reductions in serotonin function, specifically in terms of their mood and impulsivity.
Using a technique in healthy participants called acute tryptophan depletion, which decreases serotonin levels in the brain, Walderhaug and colleagues found that men became more impulsive, but did not experience any mood changes in response to the induced chemical changes. However, women in this study reported a worsening of their mood and they became more cautious, a response commonly associated with depression. The researchers also discovered that the mood lowering effect in women was influenced by variation in the promotor region of the serotonin transporter gene (5-HTTLPR).
One of the study's authors, Dr. Espen Walderhaug, explains, "We were surprised to find such a clear sex difference, as men and women normally experience the same effect when the brain chemistry is changed... Although we have the same serotonergic system in the brain, it is possible that men and women utilize serotonin differently."