Producer's Notes: Autism: Searching for Causes

It's challenging to report on an illness such as autism, which scientists and doctors are only beginning to understand (the disease was described in the 1940s) and over which there is so much debate.

There is even disagreement around the question of whether or not there has been a real increase in the number of children being diagnosed with autism in California. In our TV segment, we interview psychologist Ron Huff, director of clinical services at the Alta California Regional Center in Sacramento. In the mid-1990s, Huff sounded the alarm about an increase in the number of reported cases of autism in California. (Through California's 21 regional centers the state's Department of Developmental Services offers services to children and adults with developmental disabilities).

"In 1996 I asked the Department of Developmental Services to pull some raw data off of their statewide electronic information system. And when I saw that data it was obvious that there were a lot more kids in our system with autism than anyone else had expected,"Huff told QUEST. "By 1999 the (California) legislature decided to have the department do a formal study of the number of people who were entering the system with autism. So we looked at about 11 years of data and recognized that there was a 300 plus percent increase in the number of kids coming in with autism."

Since then, researchers have vigorously been debating whether or not there is a true increase in the number of cases. Huff believes that at least part of the increase is a true increase, in other words, that not all of the increase can be explained by factors such as more accurate diagnosis of autism, increased awareness or better availability of services. But other researchers like Kaiser Permanente epidemiologist Lisa Croen feel there isn’t enough information to conclude that even part of the cases are due to a true increase.

"Unfortunately, I don't think we really have the data, and no one really has the data right now to answer that question adequately," she told QUEST. But in her view, whether or not there's a true increase, there is indeed a crisis afoot. "It goes without question that there are definitely more people being diagnosed with autism today than ever before and that is a really big public health crisis. Estimates across the country are that one in 150 children at about 8 years of age will have a diagnosis of autism. So whether or not the increase, or how much of this increase, is really due to a true increase in occurrence, the question now is what’s causing this and what are the risk factors and that’s what we really have to concentrate on."

The research looking into factors other than genes is just beginning. The Centers for Disease Control have launched a large epidemiological study called SEED that seeks to answer the question of what the environmental causes of autism are. When researchers talk about "environmental factors" they mean this very broadly. These factors include, for example, the age of the parents. For our TV story we filmed Meghan Wallace, a four-year-old with an autism diagnosis who is participating in SEED. In Northern California, Kaiser Permanente is overseeing the research. Both children with and without autism are being enrolled. "There really has never been a large, robust, well-designed epidemiologic study that can adequately study the many possible risk factors for autism spectrum disorders," said Lisa Croen, who is one of the principal investigators on SEED.

At the same time, U.C. Davis' M.I.N.D. Institute is carrying out a smaller study into the causes of autism. It's called MARBLES and it’s funded by the EPA and the National Institute of Environmental Health Sciences. By studying pregnant women, MARBLES principal investigator Irva Hertz-Picciotto hopes to find out if there are any risk factors for autism that happen during pregnancy. In our TV story, we followed M.I.N.D. Institute personnel as they visited one of the families in the study. They had followed the mother through her pregnancy and delivery and were now taking samples from her six-month-old boy. The researchers collected everything from his dirty diapers to dust from the family's rug. In between, they asked the mom about her family's use of pesticides and cleaning products.

Hertz-Picciotto's research stemming from another M.I.N.D. Institute study has already pointed to a connection between autism and pesticides. In May of 2008, she and her colleagues reported at the International Meeting for Autism Research in London that mothers of autistic children were twice as likely as mothers of children who didn't develop autism to report that they had used household insecticides and pet shampoos for fleas or ticks. They reported using these products during a period between three months before conception and the first year of the child’s life. Other risk factors are also starting to emerge. A study by Lisa Croen and colleagues reported that paternal and maternal age are risk factors for autism. "What we found was for every 10 years of increase in the age of a mother or a father, the risk of autism went up by about 20 or 30%," Croen told QUEST.

Both the SEED and the MARBLES studies are looking at the question of whether or not childhood vaccination is a risk factor for autism. This is another issue that we talk about in our TV story. Concerned about guaranteeing that infectious diseases don't reemerge, public health officials at agencies like the CDCs state that research doesn't bear out an autism-vaccine connection. But UC Davis' M.I.N.D. Institute is taking a more nuanced approach to the question. Based on new findings by their researchers showing that the immune systems of autistic children are different than those of typically developing children, the Institute suggests that a small number of children may respond to vaccines in an atypical way. They quickly add that there isn't yet a way to determine who those children might be. Studies like SEED and MARBLES might help elucidate this and other questions about what remains a mysterious disease.