As you’ve probably noticed by now, I have a lot of opinions about mental illness.

But I don’t always have the facts to back them up.

That’s why I’m so happy about a story I came across today: Testosterone may prevent eating disorders.
It helps support what I wrote yesterday about biology being a likely reason why women are so much more prone than men to mental illness.
Researchers at Michigan State University compared girls with twin brothers to those with twin sisters. The girls who had brothers were exposed to testosterone in the womb and were less likely to develop eating disorders.

This could also help explain why men get eating disorders less often than women — although sadly, their numbers seem to be increasing. The study found that boys with a twin sister had a higher incidence of “disordered eating” than boys with a twin brother, presumably due to exposure to estrogen.

However, the story doesn’t mention whether the twin sisters were identical (from the same fertilized egg that split in two) or fraternal (from two different fertilized eggs). Identical twins have virtually the same DNA, while fraternal twins are as genetically different as singleton siblings (that is, non-multiples). It’s impossible for identical twins to be opposite-sex. So maybe genes play a role, too.

Whatever the repercussions of this study, it’s nice to have facts.