Associations between parents’ broader autism phenotype and children’s developmental difficulty scores at 6 and 12 months: A prospective study

Previous studies have investigated the associations between parents’ broader autism phenotype (BAP) in the United States and various European and Asian countries, but few studies have examined large samples to consider sex differences in children. The current study investigated whether parents’ BAP was associated with children’s developmental difficulty using the Ages & Stages Questionnaires, Third Edition (ASQ-3) at 6 and 12 months. The Japan Environment and Children’s Study (JECS) is a nationwide and government-funded birth cohort study, which began in January 2011. Among 46,438 dyads of mothers and fathers who provided complete data for the Japanese version of the Autism Spectrum Quotient (AQ-J-10) to measure BAP, the results of 31,079 dyads of mothers and fathers who also provided complete ASQ-3 data for their child were analyzed in the present study. Child sex differences were observed in ratings of developmental difficulties at 12 months, indicating that girls were rated as exhibiting less difficulty in the communication, problem solving, and personal-social domains than boys. Mothers’ BAP was strongly associated with children’s developmental difficulties at 6 and 12 months, while fathers’ BAP was associated with children’s developmental difficulty at 12 months. Fathers’ AQ-J-10 scores were associated with difficulties in girls at 12 months, and with low levels of partners’ participation in child rearing. Genetic, epigenetic, and environmental studies will be necessary to clarify the mechanisms underlying the effects of parental influences on children’s development.