Autism risk: Early medical events override genetics
- Identifying health problems in autism 1 December, London. CPD educational event for parents and professionals.
- Autism Research Should Be Financed Like Venture Capital
- London Support Group Meeting 18 October
- TA Clinical & Research newsletter for professionals – Issue 2 out!
- Century-old drug offers new hope for autism treatment
- October 2017
- September 2017
- June 2017
- May 2017
- April 2017
- March 2017
- February 2017
- January 2017
- December 2016
- May 2016
- April 2016
- March 2016
- October 2015
- June 2015
- November 2014
- September 2014
- June 2014
- January 2014
- June 2013
- March 2013
- March 2012
- January 2012
- November 2011
- October 2011
- September 2011
- June 2011
- May 2011
- March 2011
- September 2010
Study shows early medical problems and infant dysregulation predict development of autism in discordant identical twins.
A team of Swedish researchers has further illuminated the role of environmental factors in development of autism in children by looking at the medical histories of monozygotic twins where only one genetically identical sibling has symptoms and diagnosis of autism spectrum disorders.
Many twin and family studies have shown that both genetic and environmental factors play an aetiological role in autism, with the estimated role of heritable genetic factors ranging from 38-55% and the perinatal non-shared environmental factors believed to be the predominant external influence. However, this was the first study to examine the load of early medical events in autism-discordant twins.
The researchers found significantly higher rates of autism in siblings with a history of early medical events compared to their genetically identical siblings who were not exposed to such adverse events. These non-shared environmental factors included delivery and neonatal problems (e.g. foetal distress, hypoxia), minor and frequent infections (e.g. ear infections), allergy and epilepsy.
These results confirm findings of earlier studies on regulatory problems, such as excessive crying and worrying, feeding and sleeping problems, being more common in children who later received a diagnosis of autism. The authors therefore suggested that early medical adversity factors and infant dysregulation during the first year of life can be of potential help to clinicians, serving as early red flags for autism screening and detection.
Excerpts from the study:
“Single early medical factors, likely to be caused by NSE (non-shared environmental factors), that discriminated between twins in qualitative ASD discordant pairs were dysregulation during the first year of life (comprising feeding and sleeping problems, excessive crying and worrying) and birth weight …As genetic factors influence how individuals respond to different environmental exposures, limited control over the individual genetic factors has been a major weakness of most studies investigating environmental risks for ASD. As monozygotic (MZ) twins are identical on a DNA sequence level, with the exception of putative post-twinning de novo mutations, all differences in phenotypes seen in MZ twin pairs are attributable to effects of NSE.”
“Our study shows the novel finding of a cumulative environmental effect on ASD risk, when controlling for genetics. In addition, we were able to replicate earlier findings of early dysregulation as a precursor of behavioral problems and autistic traits. A previous large population-based study including over 4000 infants reported that early regulatory problems predict behavioral problems (that is, external, internal and attentional problems) later in life, and a Swedish clinical study found that regulatory issues were frequent in children later diagnosed with ASD. Our results advance these results because they demonstrate that an association between early regulation difficulties and ASD exists independent of genetic influences.”
“Our study partly supports previous results indicating low birth weight to be associated with ASD risk. We found a trend for intrauterine growth to be associated with clinical ASD and autistic traits. However, although earlier studies deemed low birth weight a consequence of genetic factors, our data indicate environmental factors as cause.”
This article is part of Treating Autism Clinical & Research Newsletter: Issue 2
Willfors C., Carlsson T., Anderlid B.M., et al. (2017) Medical history of discordant twins and environmental etiologies of autism. Transl Psychiatry. Jan 31;7(1):e1014. doi: 10.1038/tp.2016.269.
Barnevik Olsson M., Carlsson L.H., Westerlund J., et al. (2013) Autism before diagnosis: crying, feeding and sleeping problems in the first two years of life. Acta Paediatr. Jun;102(6):635-9. doi: 10.1111/apa.12229.
Hallmayer J., Cleveland S., Torres A., (2011) Genetic heritability and shared environmental factors among twin pairs with autism. Arch Gen Psychiatry. 2011 Nov;68(11):1095-102. doi: 10.1001/archgenpsychiatry.2011.76.
Losh M., Esserman D., Anckarsäter H., (2012) Lower birth weight indicates higher risk of autistic traits in discordant twin pairs. Psychol Med. May;42(5):1091-102. doi: 10.1017/S0033291711002339.
Santos I.S., Matijasevich A., Capilheira M.F., et al. (2015) Excessive crying at 3 months of age and behavioural problems at 4 years age: a prospective cohort study. J Epidemiol Community Health. Jul;69(7):654-9. doi: 10.1136/jech-2014-204568.