SNPs in the SNAP25 gene were initially [PMID 17160701] linked to intelligence but have failed to replicate [PMID 19418213].
While now suspect, the original work can be found in [PMID 16801949].
The (A;A) genotype averaged 2.84 PIQ points higher than the (A;G) genotype, which averages 2.8 PIQ points higher than the (G;G) genotype (p=0.0002). Variance in this SNP may account for 3.4% of the phenotypic variance in PIQ.[PMID 16801949]
rs363050 is in close linkage with rs353016, with r2 = 0.98, such that the rs363050(A) allele typically is linked to the rs353016(T) allele. For SNPs rs363039 - rs363043 - rs353016, respectively, the haplotype C-T-T is most associated with higher intelligence in children, whereas the haplotype C-C-T is most associated in adults (SNPs oriented as in dbSNP). [PMID 17908175]
[PMID 22762387] Supporting the generalist genes hypothesis for intellectual ability/disability: the case of SNAP25