There were no significant group differences in COMT Val158Met alleles and genotype frequencies between patients and controls, for all EDs pooled together [range of odds ratios (ORs): 0.96-1.04, p-values: 0.46-0.97, I<sup>2</sup> = 0%] and when analysing separately patients with AN (ORs: 0.94-1.04, p-values: 0.31-0.61, I<sup>2</sup> = 0%) or BN (ORs: 0.80-1.09, p-values: 0.28-0.64, I<sup>2</sup> = 0-44%).
The present study explores the effect of a functional polymorphism (Val158Met) in the catechol-O-methyltransferase (COMT) gene on the set-shifting abilities and prefrontal functional connectivity of patients with anorexia nervosa.
Meta-analytically combined evidence from the present genotypings and the literature search shows that the effect sizes are homogeneous across studies and that rs4680 is not associated with AN.
Because we were not able to support the primary hypothesis that Val158Met is a risk factor for AN, we did not perform secondary analysis of minimum body mass index (mBMI), age at onset or illness subtype (restricting or binge purging anorexia).
Catechol-O-methyltransferase (COMT) is a candidate gene for mediating susceptibility to AN since it is involved in the dopamine catabolism and because its functional polymorphism (Val/Met 158) determines high (H) and low (L) enzymatic activity alleles.