The broader autism phenotype in simplex and multiplex families.

Mothers, fathers, and siblings from 87 multiplex (M-mothers, M-fathers, and M-siblings) and 41 simplex (S-mothers, S-fathers, and S-siblings) Autism spectrum disorder families were assessed using the Broader Phenotype Autism Symptom Scale. S-mothers, S-fathers, and S-siblings showed more social interest and were more expressive in their use of nonverbal communication compared to M-mothers, M-fathers, and M-siblings. Conversational skills were also improved in S-fathers and S-siblings compared to M-fathers and M-siblings. S-siblings showed significantly lower rigidity and intense interests compared to M-siblings. The decreased number and intensity of broader autism phenotype traits observed in parents and siblings within simplex families provide behavioral evidence consistent with findings of increased de novo genetic events in simplex families.