Higher reward value of starvation imagery in anorexia nervosa and association with the Val66Met BDNF polymorphism

Recent studies support the idea that abnormalities of the reward system contribute to onset and maintenance of anorexia nervosa (AN). Next to cues coding for overweight, other research suggest cues triggering the proposed starvation dependence to be pivotally involved in the AN pathogenesis. We assessed the characteristics of the cognitive, emotional and physiologic response toward disease-specific pictures of female body shapes, in adult AN patients compared with healthy control (HC) women. Frequency and amplitude of skin conductance response (SCR) in 71 patients with AN and 20 HC were registered during processing of stimuli of three weight categories (over-, under- and normal weight). We then assessed the role of the Val66Met BDNF polymorphism as a potential intermediate factor. AN patients reported more positive feelings during processing of underweight stimuli and more negative feelings for normal- and overweight stimuli. The SCR showed a group effect (P=0.007), AN patients showing overall higher frequency of the response. SCR within patients was more frequent during processing of underweight stimuli compared with normal- and overweight stimuli. The Met allele of the BDNF gene was not more frequent in patients compared with controls, but was associated to an increased frequency of SCR (P=0.008) in response to cues for starvation. A higher positive value of starvation, rather than more negative one of overweight, might more accurately define females with AN. The Met allele of the BDNF gene could partly mediate the higher reward value of starvation observed in AN.