An analysis of the Japan Environment and Children’s Study data revealed that parents, both mothers and fathers, with higher levels of autistic traits tended to have young children (at 6 and 12 months of age) with developmental difficulties more often than their peers with lower levels of autistic traits. The paper was published in the International Journal of Behavioral Development.
Autism, or autism spectrum disorder, is a neurodevelopmental condition characterized by differences in social communication, restricted interests, and repetitive behaviors. Research consistently demonstrates that autism is highly heritable, with many genes contributing small effects. Studies of twins show higher autism concordance rates in identical twins than in fraternal twins, highlighting genetic influence.
However, genetics are not the only factor contributing to autism. Environmental factors, such as advanced parental age, prenatal exposures, or complications during pregnancy, may also interact with genetic predispositions to increase the likelihood that autism will develop. Nevertheless, children of autistic parents are at an increased likelihood of being diagnosed with autism themselves.
This connection is not limited to a formal diagnosis of autism. Parents who display traits of the broader autism phenotype, i.e., mild psychological traits related to autism not severe enough to receive a diagnosis, such as social rigidity or communication differences, are also more likely to have children with autism or with elevated levels of autistic traits.
Study author Kumi Hirokawa and her colleagues wanted to investigate whether parents’ level of autistic traits is associated with their children’s developmental difficulties at 6 and 12 months of age. These researchers analyzed data from Japan’s Environment and Children’s Study (JECS). JECS is a national, government-funded study that recruited pregnant Japanese women between 2011 and 2014. They were recruited from 15 regional centers in Japan: Hokkaido, Miyagi, Fukushima, Chiba, Kanagawa, Koshin, Toyama, Aichi, Kyoto, Osaka, Hyogo, Tottori, Kochi, Fukuoka, and South Kyushu and Okinawa.
The dataset collected in this way included data from 96,465 mothers in the second or third trimester of pregnancy and 51,898 fathers. However, after excluding participants with missing data, infants with various developmental disorders, and a number of other exclusions, a total of 31,079 mother and father pairs were available for analysis.
Study authors used data on participants’ autistic trait levels (assessed using the Autism Spectrum Quotient) and their children’s developmental difficulties at 5-6 months and 11-12 months of age (the Ages and Stages Questionnaire, Third Edition).
Results showed that girls tended to exhibit fewer difficulties in communication, problem-solving, and personal-social domains than boys. Children of mothers with pronounced autistic traits tended to have more developmental difficulties at both 6 and 12 months of age. Children of fathers with more pronounced autistic traits tended to have more developmental difficulties at 12 months of age compared to children of fathers with less pronounced autistic traits, but not at 6 months. More specifically, fathers’ autistic traits were only associated with developmental difficulties in girls at 12 months.
“In conclusion, sex differences were observed in ratings of developmental difficulties at 12 months of age, revealing that girls were rated less developmental difficulties compared with boys. Mothers’ BAP status [broader autism phenotype, the level of autistic traits] was strongly associated with child’s developmental difficulties at 6 and 12 months, indicating that children whose mothers had BAP were rated to have more severe developmental difficulties compared with the other groups. In addition, fathers’ BAP was significantly associated with children’s developmental difficulties at 12 months, especially for girls,” the study authors concluded.
The study sheds light on the links between parents’ autistic traits and children’s development. However, it should be noted that both autistic trait levels and developmental difficulties of children were reported (or self-reported) by parents, leaving room for reporting bias to have affected the results.
The paper, “Associations between parents’ broader autism phenotype and children’s developmental difficulty scores at 6 and 12months: A prospective study,” was authored by Kumi Hirokawa, Sachiko Baba, Satoyo Ikehara, Meishan Cui, Naomi Kitano, Hirofumi Nakayama, Keiichi Ozono, Hiroyasu Iso, and Japan Environment and Children’s Study Group.