Women who suffer from anorexia as well as obesity have low levels of a 'feel good' steroid and increased risk of developing depression and anxiety, a study has found. Previous research has linked low levels of the neuroactive steroid allopregnanolone - known to scientists as "allo" - to depression and anxiety, which are common mood disorders associated with anorexia nervosa and obesity. Allo is a metabolite of the hormone progesterone, one of the two major female hormones. Allo binds to receptors for the neurotransmitter gamma-aminobutyric acid (GABA) in the brain. These receptors are also the targets of anti-anxiety drugs such as benzodiazepines.
Allo works by enhancing the signal produced when GABA binds to its receptor, generally producing a positive mood and feelings of well-being. More than 50 per cent of women with anorexia nervosa have depression or anxiety, and 43 per cent of adults who are obese have depression. Low levels of allo have been linked to depression and anxiety in numerous previous studies, including people with depression and post-traumatic stress disorder. the chemical - and its impact on mood - has not been measured in anorexic or obese women. "We are beginning to see more and more evidence that low allo levels are tightly linked to depression, anxiety, post- traumatic stress disorder and other mood disorders," said Graziano Pinna, associate professor at University of Illinois at Chicago (UIC) in the US. "To see that women with anorexia nervosa and obesity have low levels adds to the picture that the role of allo is under-recognised in mood disorders," Pinna said. Researchers including those from Harvard Medical School in the US recruited 12 women with anorexia nervosa and amenorrhea whose body mass indices were less than 18.5, 12 normal-weight women with BMIs between 19 and 24, and 12 obese women with BMIs at 25 or higher. None of the women had received a diagnosis of depression or ever took antidepressants. The average age of the participants was 26 years old. Participants completed questionnaires to assess for depression and anxiety and had blood drawn. Blood measurements of allo and other hormones were performed by Pinna's lab at the UIC. The study, published in the journal Neuropsychopharmacology, found that in women with anorexia nervosa and in obese women, blood levels of allo were 50 per cent lower than they were in women with normal BMIs, and women who were clinically obese had allo levels about 60 per cent lower than women with normal weights. They also found that levels of allo in all participants correlated with the severity of their depression and anxiety symptoms as measured by the questionnaires. Participants with lower levels of allo had greater severity of depression symptoms. "Depression is an incredibly prevalent problem, especially in women, and also particularly at the extremes of the weight spectrum," said Karen Miller, professor at Harvard Medical School in the "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," said Miller.