Genes may play a greater role in the development of autism spectrum disorder (ASD) than previously thought, according to a new study, which found that children whose family histories include mental and neurologic disorders are at an increased risk for ASD.
The study, published in the JAMA Network Open, utilized the population-based Stockholm Youth Cohort—a cohort of more than 500,000 young persons aged up to 17 years in a single county in Sweden.
The registry tracked children in the cohort to a mean of 14 years and found overall prevalence of ASD to be 0.4% with intellectual disability, and 1.5% without.1 Researchers then delved into the family histories of those participants identified with ASD and found that 63.1% of the cohort that was identified to have ASD with an intellectual disability also had a parent with a history of mental and/or neurologic disorders, compared with 45.4% of participants without ASD.
Autism spectrum disorder affects 1% to 2% of the population worldwide, and children typically are diagnosed around age 8 years, according to the report, with about one-quarter of those with an ASD diagnosis also affected by some degree of intellectual disability. Family history of ASD is the strongest known risk factor, according to the researchers, based on twin studies, but this report indicates that other mental or neurologic disorders may be linked to ASD risk as well.
“Autism spectrum disorders with and without intellectual disability showed different patterns of familial association,” the report notes. “For the disorders that were associated with both, their associations with ASD with intellectual disability tended to be weaker, suggesting that family history of mental and neurological disorders was more relevant for higher-functioning ASD.”
Researchers calculated odds ratios for having first-degree relatives with ASD with no intellectual disability, and those ratios were 4.1 for participants with ASD with intellectual disabilities, and 9 for participants with ASD and no intellectual disabilities. For those with first-degree relatives with an ASD diagnosis and intellectual disabilities, the odds ratio was 14.2 for children in the cohort with ASD plus intellectual disabilities, and 3.8 for participants with ASD and no intellectual disabilities, according to report data.
Specifically looking at other mental health disorders and their relation to ASD, the research team found high ratios for ASD in children whose relatives had attention-deficit/hyperactivity disorder, schizophrenia and nonaffective psychotic disorders, depression, bipolar disorder, and personality disorders. Neurologic disorders with a strong link to ASD in a family member included cerebral palsy and epilepsy, according to the report.
Researchers found links between ASD and family histories of mental or neurologic disorders as far as fourth-degree family members, but not that the more closely related an affected family member was, the higher the odds of an ASD diagnosis in the child. The study authors also note that overall, children with ASD without intellectual disabilities were more significantly associated with relatives with mental health disorders, whereas children in the cohort who had ASD with intellectual disabilities more often had neurologic diseases in their family histories.
Why family matters
Brian K. Lee, PhD, associate professor of Epidemiology and Biostatistics at the Drexel University Dornsife School of Public Health, Philadelphia, Pennsylvania, and co-author of the study, says this research shows that a family history of multiple common psychiatric and neurologic conditions—not just ASD or in first-degree relatives—is associated with an increased risk of ASD.
“Family history of ADHD and intellectual disability were relatively strongly associated with an ASD diagnosis. For example, ADHD in a first-degree relative was associated with 4.7 times higher odds of ASD without intellectual disability in a child, while intellectual disability in a first-degree relative associated with 7.6 times higher odds of ASD with intellectual disability in a child,” Lee says.
Lee adds that whereas this was a single epidemiological study that doesn’t really translate to the individual patient level, he hopes that pediatricians may use future findings along this same line to look at risk factors. These associations may be used for early identification and intervention, he says.
“Ultimately, my hope for the future is that with a stronger evidence base from multiple study replications, it may be possible to identify at an early stage the children at higher risk of receiving an ASD diagnosis so they can receive appropriate interventions,” Lee says. “Family history is just one piece of information that may help inform this risk.”
1. Xie S, Karlsson H, Dalman C, et al. Family history of mental and neurological disorders and risk of autism. JAMA Netw Open. 2019;2(3):e190154. Available at: https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2726710. Accessed April 15, 2019.