Parents of a child with autism are understandably concerned about the likelihood that their subsequent children will be affected. Autism Speaks and its legacy organization, the National Alliance for Autism Research, have been funding research on younger siblings for nearly 15 years– to help us better understand their development.
In 2003, we began organizing and co-funding a very special collaboration—the High Risk Baby Siblings Research Consortium—in partnership with Eunice Kennedy Shriver National Institute for Child Health Development.
This week, we announced the results of the consortium’s largest ever siblings study. The researchers followed younger brothers and sisters from infancy through the preschool period, when autism diagnosis becomes possible. The study revealed a markedly higher risk among younger siblings than had been previously reported.
As the autism community absorbs the news, let me give you some background on the quality and importance of this research—and what it means for parents.
Our “Baby Sibs” researchers are an international network of clinical researchers who have been pooling information from studies of affected families in 21 sites in the US, Canada, Israel and the UK. Alycia Halladay, Autism Speaks director of research for environmental sciences, and Andy Shih, vice president of scientific affairs, have led the consortium from the start and continue to coordinate its activities.
In the study making headlines this week, the consortium researchers assessed 664 infants. Each had at least one older sibling diagnosed with an autism spectrum disorder (ASD). They found that 1 in 5 babies with an older sibling on the spectrum will likewise be affected—more than double previous estimates. The rate was higher among younger brothers—1 in 4, versus 1 in 9 for younger sisters. And autism affected nearly 1 in 3 infants with more than one older sibling on the spectrum. (Previous estimates came out of much smaller and sometimes less reliably conducted studies.)
So what does this mean for parents?
If you have an older child on the spectrum and you are concerned about your infant, talk to your pediatrician about your baby’s risk and your desire for close monitoring. And if you have any concerns about your child’s development, don’t wait. Speak with your doctor about screening.
Here are links to a number of helpful resources:
* Recent research funded by Autism Speaks shows that a one-page baby-toddler checklist can be used effectively as early as 12 months as an initial screen for autism and other developmental disorders. The screener is available here.
* As a parent or caregiver, one of the most important things you can do is learn the early signs of autism and understand the developmental milestones your child should be reaching. You can see the Learn the Signs guidelines on our website, here.
* Finally, families with one or more children on the spectrum can contact their nearest “Baby Sibs” consortium researcher if they would like to participate in this important research. The list is on our website, here.
By monitoring your infant closely and promptly beginning intervention if signs of autism appear, you can ensure that your child will have the best possible outcome.
Autism risk ‘high’ for kids with older sibling with the disorder. Autism Speaks’ Alycia Halladay, Ph.D., provides perspective of NPR’s All Things Considered. To listen to the segment, visit here.
This post is by Guest Blogger Rebecca Schmidt, Ph.D., Assistant Professor, Department of Public Health Sciences, UC Davis and first author on the research described below.
UC Davis researchers conducted a study comparing children with autism to children without autism, all aged 24-60 months, to see whether their mothers differed in terms of taking prenatal vitamin supplements before and during pregnancy. Combined effects of maternal vitamin intake and genotypes affecting a key metabolic pathway known as one-carbon metabolism were also examined.
In this retrospective study, mothers of children with autism were significantly less likely than those of typically developing children to report having taken prenatal vitamins during the three months before and the first month of pregnancy. Prenatal supplement use was similar across the other months of pregnancy. Maternal education and the child’s birth year were accounted for; however, because the mothers were asked about their vitamin use years after their pregnancy, and after their child’s developmental status was known, recall bias could have influenced the results.
The researchers postulate that folic acid, the synthetic form of folate or vitamin B9, and the other B vitamins in prenatal supplements, are probably protecting against deficits in early fetal brain development. Folate is known to be critical for proper neurodevelopment and studies have found that supplemental folic acid has the potential to prevent up to 70 percent of neural tube defects.
Interaction effects were also observed between periconceptional prenatal vitamin intake and maternal and child genotypes. When a mother did not report taking prenatal vitamins and she or her child had genotypes associated with less efficient folate-dependent one-carbon metabolism, the child was at much greater risk for autism. These findings demonstrate gene/environment interactions in autism.
Maternal genes involved in significant interaction effects included the well-studied methylenetetrahydrofolate reductase (MTHFR) folate metabolism gene and vitamin B6-dependent cystathionine-beta-synthase (CBS), which is an enzyme involved in metabolizing protein building-blocks that contain sulfur. The child’s catechol-O-methyltransferase (COMT) gene was associated with more than seven times the risk for autism when in combination with no maternal periconceptional prenatal vitamin intake, compared to children with other genotypes whose mothers did report periconceptional prenatal vitamin intake. The COMT enzyme, responsible for the degradation of the neurotransmitter dopamine and well-known for its association with schizophrenia, is active during early neurodevelopment. Structural and functional brain differences have been described across COMT genotypes, particularly in the hippocampus and prefrontal cortex, regions previously shown to be affected in individuals with autism.
These findings are the first to suggest a concrete step women can take that may reduce the risk of having a child with autism. Future research is warranted to replicate these findings and enhance understanding of potential mechanisms.