FXR2 and major depressive disorder: The functional plausibility of an FMR1 association with depression is supported by its position on the non-autosomal X chromosome, by reports of fragile X premutation carriers being susceptible to depression [20-24], by well-known effects of FMR1 on brain synaptic functions [18,19], and by the interesting nominally-significant association in FXR2 rs7211847, P=0.0165 in Sleep Clinic and DSPS samples meta-analysis) (see Additional file 1).