Two new studies have confirmed that changes to the environment influence the possible development of autism in children.
One study examined the impact of selective serotonin reuptake inhibitors (SSRIs) on the development of autism spectrum disorder (ASD) symptoms. In this study published in the Journal of Autism and Developmental Disorders, 750,000 births were analyzed from 1997-2006. They found that approximately 1.5 percent of children born to women who had taken a selective serotonin reuptake inhibitor (SSRIs) were diagnosed with ASD, compared to about 0.7 percent of children born to an otherwise similar group of women not taking the medication.
“We found a two-fold increased risk for ASD associated with in utero exposure to SSRIs compared to the unexposed reference group” said lead author Nicole Gidaya, PhD. “More importantly, in our analysis we accounted for under-reporting of maternal depression in the register. This suggests that under-reporting of the confounder, maternal depression, may be a limitation in approaches previously used in the other studies.”
“As we complete research in our attempts to understand autism’s causes we continue to realize that there are likely many genetic and non-genetic contributors,” said Craig Newschaffer, PhD, director of the A.J. Drexel Autism Institute and professor in Drexel’s School of Public Health, and the study’s senior author. “We must begin trying to map these multiple risk factors on to common pathways, so that these pathways can be a focus in our effort to prevent the impairment associated with ASD. Pathways involving the brain’s serotonin system are still one viable candidate.”
Another collaborative study involving Scientists from the University of Cambridge and the Statens Serum Institute in Copenhagen, Denmark discovered that children who later develop autism were also exposed to elevated levels of steroid hormones (for example testosterone, progesterone and cortisol) in the womb. The results of this study were published in the journal Molecular Psychiatry. Steroid hormones are highly relevant to the development of autism as they influence the process of how instructions in the genetic code are translated into building proteins. The researchers have hypothesized that altering this process during periods when the building blocks for the brain are being laid down may be particularly important in explaining how genetic risk factors for autism get expressed.
In this study 19,500 amniotic fluid samples from individuals born between 1993-1999 stored in a Danish biobank were analyzed. In Denmark the amniotic fluid was collected during the 15-16 week pregnancy stage during amniocentesis. This pregnancy stage is a critical period for early brain development and sexual differentiation. Fluid samples from 128 males later diagnosed with an autism spectrum disorder condition were identified. The analysis of the amniotic fluid consisting of researchers looking at 4 key ‘sex steroid’ hormones that are each synthesized, step-by-step from the preceding one, in the ‘sex steroid’ pathway: progesterone, 17α-hydroxy-progesterone, androstenedione and testosterone. They also tested the steroid hormone cortisol that lies outside this pathway.
The findings of this study reflected that levels of all steroid hormones were highly associated with each other and most importantly, that the autism group on average had higher levels of all steroid hormones, compared to a typically developing male comparison group.
Professor Baron-Cohen commented on the study: “This is one of the earliest non-genetic biomarkers that has been identified in children who go on to develop autism. We previously knew that elevated prenatal testosterone is associated with slower social and language development, better attention to detail, and more autistic traits. Now, for the first time, we have also shown that these steroid hormones are elevated in children clinically diagnosed with autism. Because some of these hormones are produced in much higher quantities in males than in females, this may help us explain why autism is more common in males.
These new results are particularly striking because they are found across all the subgroups on the autism spectrum, for the first time uniting those with Asperger Syndrome, classic autism, or Pervasive Developmental Disorder Not-Otherwise-Specified. We now want to test if the same finding is found in females with autism.”
S Baron-Cohen, B Auyeung, B Nørgaard-Pedersen, D M Hougaard, M W Abdallah, L Melgaard, A S Cohen, B Chakrabarti, L Ruta, M V Lombardo. Elevated fetal steroidogenic activity in autism. Molecular Psychiatry, 2014; DOI: 10.1038/mp.2014.48
Nicole B. Gidaya, Brian K. Lee, Igor Burstyn, Michael Yudell, Erik L. Mortensen, Craig J. Newschaffer. In Utero Exposure to Selective Serotonin Reuptake Inhibitors and Risk for Autism Spectrum Disorder. Journal of Autism and Developmental Disorders, 2014; DOI: 10.1007/s10803-014-2128-4