Environmental factor to blame for autism?

Washington: Researchers have said that environmental factors are more important than previously believed in understanding the causes of autism, and equally as important as genes. The study also shows

By: Editorial Team | | Updated: October 8, 2014 10:26 am

Washington: Researchers have said that environmental factors are more important than previously believed in understanding the causes of autism, and equally as important as genes. The study also shows that children with a brother or sister with autism are 10 times more likely to develop autism; 3 times if they have a half-brother or sister; and 2 if they have a cousin with autism, providing much needed information for parents and clinicians for assessing individual risk.

The study led by researchers at King’s College London, Karolinska Institutet in Sweden and Mount Sinai in the US, looked at over 2 million people. Using Swedish national health registers, the researchers analysed anonymous data from all 2 million children born in Sweden in between 1982 and 2006, 14,516 of which had a diagnosis of ASD. The researchers analysed pairs of family members: identical and non-identical twins, siblings, maternal and paternal half-siblings and cousins. (Read: 6 tips for parents to deal with autistic children)

The study involved two separate measures of autism risk – heritability, which is the proportion of risk in the population that can be attributed to genetic factors; and Relative Recurrent Risk which measures individual risk for people who have a relative with autism. Environmental factors are split into ‘shared environments’ which are shared between family members (such as family socio-economic status), and ‘non-shared environments’ which are unique to the individual (such as birth complications or maternal infections or medication during the pre and perinatal period). In this study, factors which are unique to the individual, or ‘non-shared environments’ were the major source of environmental risk. (Read: 10 misconceptions about children with autism busted!)

In the other part of the study, the researchers looked at individual risk. In the general population, autism affects approximately 1 in 100 children. The researchers found that children with a brother or sister with autism were 10.3 times more likely to develop autism; 3.3-2.9 times if they had a half-brother or sister with autism; and 2.0 times if they had a cousin with autism. (Read: 10 things every child with autism wishes you knew)

The study has been published in the JAMA.

What is autism?

Autism is a developmental disorder wherein the normal brain development is disrupted very early in life. Autistic spectrum disorder is an umbrella term to encompass all the neurodevelopmental disorders in children. Autism impacts communication, behaviour and social relationships and approximately 67 million people worldwide are estimated to be affected by it. It is the fastest growing global disorder. In this condition, cognition skills are hampered because of altered nerve cells, although the causative factor is unknown. A combination of genetics and the environment have been found to contribute to the development of autism. Symptoms differ from one child to the other. Autistic children have varying degrees of impairment in communication and socialization, and have various behavioural problems in the form of repetitive behaviour, restricted play interests and sometimes very unusual interests.

Autism can be diagnosed in many cases by 3 years of age based on the symptoms the child shows. There is no cure for autism. But early diagnosis and early intervention with therapies does improve the long term outcome in autism. The various therapies recommended are occupational therapy, communication therapy and behavioural therapy. Medications are used to improve some of the symptoms like irritability, hyperactivity and aggressive behaviour when they do not responded to other therapies. (Read: Treating autism – therapies and treatments)

With inputs from ANI

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Published : May 5, 2014 10:51 am | Updated:October 8, 2014 10:26 am

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