Women who struggle with anorexia nervosa or obesity exhibit low levels of a neuroactive steroid known as allopregnanolone, a metabolite of the hormone progesterone, according to a new study published in the journal Neuropsychopharmacology.
Previous studies have linked low levels of allopregnanolone (allo) to depression and anxiety, which are common mood symptoms in both anorexia and obesity. Low levels of allo have also been found in people with post-traumatic stress disorder (PTSD). But until now, the chemical and its impact have not been measured in anorexia or obese women.
Allo binds to receptors and enhances the signal of the neurotransmitter gamma-aminobutyric acid (GABA), generally producing a positive mood and feelings of well-being. More than 50 percent of women with anorexia nervosa have depression or anxiety, and 43 percent of adults who are obese have depression.
“Depression is an incredibly prevalent problem, especially in women, and also particularly at the extremes of the weight spectrum,†said study leader Dr. Karen Miller, professor of medicine at Harvard Medical School.
The researchers found that in women with anorexia nervosa and in obese women, blood levels of allo were 50 percent lower than they were in women with normal BMIs. Women who were clinically obese had allo levels approximately 60 percent lower than normal-weight women. In addition, levels of allo in all participants correlated with the severity of their depression and anxiety symptoms as measured by the questionnaires.
We are beginning to see more and more evidence that low allo levels are tightly linked to depression, anxiety, PTSD, and other mood disorders. To see that women with anorexia nervosa and obesity have low levels adds to the picture that the role of allo is under-recognized in mood disorders.
The hope is that a greater understanding of mechanisms contributing to these disorders—including abnormalities in the regulation of hormones and their neuroactive metabolites—may lead to new-targeted therapies in the future.