For the aperiodic exponent, there was no significant difference between the two TDC cohorts, however, there was a significant difference between the STXBP1 syndrome cohorts from the Netherlands and Denmark [t(9) = 2.9, p = 0.02], however, not after Bonferroni correction (Supplementary Figure 5D). This evidence concerns the gene STXBP1 and Down syndrome.