Even though the analysis method using subsets of ASD families may be limited by chance findings due to reshuffling of the families and by decreased power due to reduction of sample size, the two most significant linkage signals on chromosomes 11 and 15 (both were reported in the previous studies of autism [28,33] and one [on chromosome 15] was linked to schizophrenia [52,53]) show that it is still a potentially useful method to overcome genetic heterogeneity. Autism spectrum disorder families with IQ ≥ 70 may represent a more genetically homogenous group, while the families that have rare single gene disorders, undetected chromosomal abnormalities, or de novo copy number variations tend as a whole to have lower IQ (66) and including them in a linkage analysis may reduce power.
