Chuck Bednar for redOrbit.com – Your Universe Online
Women are two times more likely to be diagnosed with depression than men, and new research appearing in the journal Biological Psychiatry suggests that their sex hormones may be to blame.
According to the researchers from the Medical University of Vienna behind the study, previous scientific studies have proven that female sex hormones have a strong effect on the psyche. Also, phenomena such as the postpartum blues and mood swings that occur prior to menstruation on a regular basis further confirm this association, the study authors claim.
Conversely, the male sex hormone testosterone has been found to impact a person’s mood and emotions in a positive way, and now the authors believe that they have discovered the biological mechanism behind this relationship – which could also help explain why men tend to suffer from depression more often as they grow older and their testosterone output falls.
Rupert Lanzenberger from the university’s Department of Psychiatry and Psychotherapy and his colleagues claim to have demonstrated for the first time that testosterone increases the number of serotonin transporters (proteins) in the human brain. Those proteins regulate the concentration of serotonin, and are also the target for antidepressants, the researchers said.
To study this possible effect of testosterone, Lanzenberger and his colleagues used cross-sex steroid hormone treatment of transsexuals who had been seeking gender reassignment therapy. They recruited 33 transsexuals, and used positron emission tomography (PET) both before and after the start of treatment in order to gauge its impact on serotonin transporter levels.
As study author Georg Kranz explained, “Transsexuals are people who feel that they are living in the wrong body and who therefore want high doses of opposite gender hormone therapy to adapt their appearance to that of the other gender. Genetic women are given testosterone, while genetic men are given oestradiol and medications to suppress testosterone production.”
Kranz, Lanzenberger and their colleagues found that serotonin transporter levels in the brain were significantly higher after just four weeks of hormone therapy with testosterone, and that the levels increased further if therapy continued beyond that point. In addition, they also found a link between testosterone levels in the blood and the concentration of serotonin transporters.
“The study has shown that testosterone increases the potential binding sites for commonly prescribed antidepressants such as SSRIs in the brain and therefore provides major insights into how sex hormones affect the human brain and gender differences in psychiatric illnesses,” said Siegfried Kasper, head of the university’s Department of Psychiatry and Psychotherapy.
“Given the central role of the SERT [serotonin reuptake transporter] in the treatment of depression and anxiety disorders,” the study authors wrote, “these findings may lead to new treatment modalities and expand our understanding of the mechanism of action of antidepressant treatment properties.”