FTO and major depressive disorder: A single-nucleotide polymorphism (SNP) in FTO (rs9939609) that explains 0.34% of the variance in obesity6 was found to confer protection against MDD in 6561 depression cases and 21 932 controls.7 However, the rs9939609 A allele was found to increase risk for MDD in an independent sample of 1544 cases and 2806 controls, although after adjustment for BMI this was no longer significant.