An interesting study… 

This study shows that serum brain-derived neurotophic factor (BDNF) is significantly lower in women with anorexia nervosa (AN) compared with women without an eating disorder and women recovered from AN. While recovery from AN is difficult to define, BDNF may emerge as a useful biomarker of AN and of recovery from AN.

Finding biomarkers for AN and recovery from AN can help improve diagnostic accuracy and help better identify individuals who have recovered from AN. BDNF polymorphisms have not only previously been associated with AN {1}, but the BDNF-specific receptor neurotrophic tyrosine kinase receptor type 2 has also been associated with temperament characteristics and low BMI in individuals with eating disorders {2}. The current study evaluated serum BDNF levels in women with AN (n=29), women without an eating disorder (n=28) and women recovered from AN for 1 or more years (n=18). In addition, set-shifting ability was also evaluated in all 3 groups using the Wisconsin Card Sorting Task (WCST). Age was similar among all three groups, and women with AN and recovered women did not differ in lowest lifetime BMI. Women with AN had lower serum BDNF than controls and recovered women. Overall, there was a positive association between BDNF and BMI. BDNF was inversely correlated with the eating concerns, shape concerns, weight concerns, and global scale on the Eating Disorder Examination Questionnaire and on the depression and anxiety sections of the Hospital Anxiety and Depression Scale. Women with AN made more mistakes on the WCST than control women, but BDNF level was not associated with performance on the WCST. Set-shifting was not impaired in individuals recovered from AN. The current study excluded healthy control women with a BMI below 19 or over 26 thereby excluding constitutionally thin and obese women. It is plausible that BDNF is related more to BMI or the starvation state than to AN per se. However, the relationship between BDNF and BMI is unclear as the results from one study indicate lower levels of BDNF in morbidly obese individuals compared with obese individuals {3}. Including constitutionally lean and obese women in future studies may help clarify the relationship among BDNF, BMI, and AN. BDNF may be a useful biomarker in the underweight AN state and in indexing recovery from AN. However, it is important to first ensure that BDNF is in fact associated with AN and not strictly BMI or other indices of starvation.

References: {1} Ribases et al. Mol Psychiatry 2003, 8:745-51 ]. {2} Ribases et al. Mol Psychiatry 2005, 10:851-60 ]. {3} Bullo et al. Eur J Endocrinol 2007, 157:303-10 ].