In 1990, 6 out of 10,000 children were diagnosed with autism by age 5 in California. In 2001, it was 42 in 10,000 — a 600 per cent spike.
For the past 10 years, Irva Hertz-Picciotto has tried to discover what environmental factors could account for that staggering increase. And she thinks not enough other researchers are trying to do the same.
“From the perspective of funding, a lot more attention has gone to the genetics,” she says.
By comparison, “the amount of money that’s gone towards environmental research is very small.”
Hertz-Picciotto, professor of epidemiology at the UC Davis MIND Institute, presented some of her research at the Geneva Centre for Autism International Symposium in Toronto on Thursday. For the past decade, she has been involved in a major study that followed more than 1,600 California families with children who have autism, other developmental disabilities, or no developmental disabilities at all.
While there are no definitive environmental causes of autism, she and her colleagues have uncovered some intriguing data.
The team has taken reams of biological specimens — hair samples, blood samples, and the like — from the children and conducted interviews to determine factors like the family’s diet, lifestyle, and mother’s reproductive health.
In one analysis, they examined whether children with autism had more heavy metal toxicity than the typically developing children. In fact, the reverse was true: neurotypical children had slightly higher levels of mercury in their system.
As it turned out, those children tended to consume more fish. Once that was controlled for, autistic and non-autistic children had the same heavy-metal levels. Parents, the study suggested, should probably save money that would have been spent on expensive chelation, or heavy-metal elimination, therapies.
The study did find, however, that mothers of children with autism were less likely to have taken folic acid in the months before they conceived. Children whose genes don’t take up folic acid efficiently, and whose mothers didn’t take folic acid at all during early pregnancy, were seven times more likely to have autism than kids who had good genes and whose mothers took folic acid.
Living close to a freeway was also correlated with higher incidences of autism.
In 2009, Hertz-Picciotto published a study that tried to account for the huge spike in autism diagnoses by looking at changing diagnostic criteria and other factors like maternal age.
At most, they could only explain half of the increase, according to their data.
Studying the environmental causes of autism has not been popular, she says, because so many people equate their work with the famously flawed studies that trumpeted vaccines as a cause of autism, which led parents astray for years.
Other studies that looked at autism diagnosis and seasonality also raise interesting questions. According to a study conducted by one of Hertz-Picciotto’s students, there is a small but significant correlation between the month of conception and a child’s risk of developing autism: of the cases they examined, babies conceived in December, January, February or March had a slightly higher risk of being diagnosed with autism.