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. This evidence concerns the gene FTO and depressive symptom measurement.