Data from more than 2 million children in Sweden suggest that inflammatory bowel disease among the parents, and especially the mothers, may be associated with autism among children. Nevertheless, the study shows that shared genetic background does not appear to explain the association and may instead implicate factors related to symptoms of inflammatory bowel disease during pregnancy.
Data from more than 2 million children in Sweden suggest that inflammatory bowel disease among the parents, and especially the mothers, may be associated with autism among children. Nevertheless, the study shows that shared genetic background does not appear to explain the association and may instead implicate factors related to symptoms of inflammatory bowel disease during pregnancy.
Researchers have long known that inflammatory bowel diseases are associated with autism. People with autism have inflammatory diseases more often than the general population.
In addition, various research results have indicated that parents’ inflammatory bowel disease or insufficient nutrients during fetal development may be associated with the child developing autism.
This was the starting-point for a study of a nationwide population-based cohort investigating whether chronic inflammatory bowel diseases such as Crohn’s or ulcerative colitis among the parents could be associated with a child’s autism.
“Inflammatory bowel disease among parents may be associated with children developing autism. Nevertheless, our studies were designed to improve understanding of the associations between inflammatory bowel disease and autism and cannot be used to create clinical guidelines or make public health decisions. Further studies are needed before recommendations can be considered,” explains a researcher behind the study, Aws Sadik, an academic clinical fellow at the University of Bristol, United Kingdom.
The research has been published in Nature Medicine.
Data from 2.3 million children
The researchers analysed population data for Sweden from 1987 to 2010. During that period, 2.8 million children were born in Sweden, of which 2.3 million were included and followed up to 2016. About 45,000 children (nearly 2%) were diagnosed with autism during the follow-up.
Using the same registries, the researchers also determined whether the children’s mother or father had been diagnosed with inflammatory bowel disease. They then compared the prevalence of autism among children of parents with and without inflammatory bowel disease while considering other factors known to influence the development of autism.
The results showed that autism was diagnosed more often among children whose mothers had been diagnosed with inflammatory bowel disease.
Genetics does not explain the association
The researchers also examined the factors that link parental inflammatory bowel disease and child autism by investigating large data sets of genes that are associated with autism and inflammatory bowel disease.
Some common genetic variants predispose to the development of inflammatory bowel disease and others autism.
The researchers used data sets containing data on 59,957 people with inflammatory bowel disease and 46,350 people with autism and examined how genetic variants are associated with inflammatory bowel disease and autism, but they found no evidence of an underlying genetic association.
Then the researchers estimated how genetics contributes to inflammatory bowel disease among 7,348 mothers and 7,503 children in the Avon Longitudinal Study of Parents and Children in the United Kingdom. They found that autistic traits among children were associated with genetic susceptibility to inflammatory bowel disease among mothers but were not associated with genetic susceptibility to inflammatory bowel disease among the children.
Autism is part of the variation between people
Finally, the researchers used two-sample Mendelian randomisation analysis to substantiate their findings.
This approach aims to sidestep some of the potential biases in other studies by taking advantage of the principles that genetic variants are fixed at conception and not generally linked to associations in the general population.
The researchers found that genetic predisposition to inflammatory bowel disease affected autism but not the other way around. This supports the other results.
“Overall, the analysis suggests that autism among children probably results from something during fetal development rather than a shared genetic risk between these two diseases,” says Aws Sadik.
According to Aws Sadik, the study indicates that especially maternal inflammatory bowel disease is associated with the child’s autism and that this is not caused by a shared genetic basis.
“We need to understand better the various health conditions associated with autism so that we can reduce or treat these conditions and improve the quality of life of people with autism. However, we do not describe autism as a problem but more as part of the natural variation between people,” concludes Aws Sadik.
