Genetic Gender Difference for Depression
> 11/30/2007 2:27:24 PM

We have long known that women are twice as likely to suffer from depression, but it was not clear whether this risk is elevated by genetic, social, or hormonal factors. While a complex combination of factors may be responsible, the fact that gene expression plays at least some role was confirmed as far back as 1999 by a twin study. The twin study showed that while genes elevated the risk of depression in both men and women, they were less important than environment for men. Does this mean that the male mind is more vulnerable to external influences, or that depression genes express themselves differently in the two sexes? A study this week by researchers at Duke University has just shed some light on this genetic sex difference.

With any widespread gene with harmful effects, it is useful to inquire into whether it may have a beneficial flip-side. While random deleterious mutations are common, they rarely spread far in the gene pool. Conforming to this expectation, Duke researchers found that the two alleles of the 5-HTT gene had opposite effects in men and women, meaning that their risk was balanced in the population. Females with the short allele face the highest danger of depression, while men are put in jeopardy by the long allele. This is only one gene and many others may contribute to mood disorders, so we should continue looking for other two-sided genes to explain the sex disparity. 

Further research is required to discover exactly how the 5-HTT gene has variable effects on the brain. 5-HTT is a serotonin transporter, so the first thing researchers should look for is a differing stress response in the sexes mediated by serotonin levels. The more that we understand individual responses to trauma, the better doctors and patients will be able to anticipate depressive episodes and take precautions to prevent them.


The 2x difference may be nothing more than a product of the way depression is subjectively defined by psychiatrists and or reflective of the the fact men are more likely to be reticent re talking about feelings of depression.
Posted by: TJ 11/30/2007 3:16:41 AM

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