There was also a statistical trend towards lower FMRP levels in the FXS + ASD subgroup with mild + moderate ID when compared with FXS-only with mild + moderate ID (N = 5, 3.3 ± 1.4 versus N = 10, 6.1 ± 4.3; p = 0.075, Welch’s t-test), but no differences when groups with severe ID with and without ASD were compared. This evidence concerns the gene FMR1 and fragile X syndrome.