Awareness of ASD has grown dramatically in the last two decades. At the same time, scientists have been working to unravel the causes of ASD, which is estimated to affect nearly 1 in 89 children in India, according to a recent study by INCLEN, the International Clinical Epidemiology Network Trust. The autism spectrum, as the name suggests, is a wide range of difficulties in social communication and behaviour, which can last a lifetime.
A child’s environment may also play in development of ASD. These environmental factors might act as a trigger in a genetically susceptible individual and may set off autism. Environmental factors are notoriously challenging to measure, since each person’s physical and social environment is unique and constantly changing. ASD researchers are searching for which elements of the prenatal and early childhood environment may contribute to the risk for autism.
Can a mother’s infection during pregnancy play a role? Several studies have investigated whether mothers who have rubella or cytomegalovirus, known as CMV, during pregnancy are at a higher risk for delivering a child with ASD, especially if the mother was hospitalized.
What about the ages of a child’s parents? A recent large population study of over 5,700,000 participants from Australia, Denmark, Israel, Norway, and Sweden, including 30,902 cases of ASD, found that older parents have a higher risk for having a child with ASD, as do teenage mothers and couples with a large age gap. Yet it is unclear how exactly a parent’s age translates into ASD risk, and the majority of children born to older parents do not have ASD.
The Child Neurology Division, Department of Pediatrics, AIIMS in New Delhi has led several research projects into risk factors for ASD. A recent study at AIIMS found that while both ASD and typically-developing children who visited the hospital’s outpatient department had vitamin D insufficiency on average, the ASD children had significantly lower vitamin D levels. Another study found that that heavy metals — mercury, lead, zinc, arsenic, and cadmium — did not show significant association with diagnosis of autism.
In Norway, researchers at the Norwegian Institute of Public Health and University of Oslo are studying the Autism Birth Cohort (ABC) born between 1999 and 2008, as part of the nationwide Norwegian Mother and Child Cohort Study. The ABC study will help link information about how these children develop to genetic changes and other biomarkers. ABC is one of several ongoing studies of autism and child neurodevelopment with affiliated researchers both in Norway and abroad.
What scientists do agree upon is that genetic and environmental factors mix together to influence a child’s risk for developing ASD. Dedicated studies that look into the etiopathogenesis are currently being carried out for a better understanding of the disorder that may ultimately help in managing these children in a better way.
This article is published with contribution from the Child Neurology Division, Department of Pediatrics, AIIMS New Delhi