Causation: Take Your Pick

One reason why there is so much debate and confusion about autism is that research on causation seems to point in multiple directions. In the past week alone, news accounts have mentioned findings on air pollution, brain overgrowth, antidepressants, and low birth weight.

From The Wall Street Journal:

"The evidence is growing that air pollution can affect the brain," says medical epidemiologist Heather Volk at USC's Keck School of Medicine. "We may be starting to realize the effects are broader than we realized."

Reviewing birth records, Dr. Volk and her colleagues calculated that children born to mothers living within 1,000 feet of a major road or freeway in Los Angeles, San Francisco or Sacramento were twice as likely to have autism, independent of gender, ethnicity and education level, as well as maternal age, exposure to tobacco smoke or other factors. The findings were published this year in the journal Environmental Health Perspectives.

"Based on our data, it looks like air pollution might be a risk factor for autism," Dr. Volk says. Still, there are so many possible genetic and environmental influences that "it is too soon for alarm," she says.

From AFP:

A post-mortem analysis of half a dozen autistic boys showed that their brains were heavier and contained many more neurons than counterparts without the disorder, US researchers said Tuesday.

The study, while small, suggests that brain overgrowth may be occurring in the womb, according to the findings published in the November 9 issue of the Journal of the American Medical Association.

From Cox Newspapers:

As scientists strive to find what's behind a spike in autism, especially in boys, a new study has raised the possibility that antidepressants taken by their mothers may be a culprit, a finding that has set off concern for women and their doctors.

Rodents exposed to the antidepressant Celexa displayed autismlike changes in their brain structure and their pups' behavior, especially the males, according to the study, published last month in Proceedings of the National Academies of Sciences.

Celexa is a commonly prescribed antidepressant in a class that includes Lexapro, Zoloft and Prozac.

Another study, published in July in Archives of General Psychiatry, found that autistic children were twice as likely as other children to have been exposed to antidepressants before birth. First-trimester exposure created nearly four times the risk.

From The Washington Post:

THE QUESTION Might the tiniest of newborns face a bigger chance of developing autism?

THIS STUDY involved 623 children who were born in the mid-1980s weighing 4.4 pounds or less. Their health was assessed periodically, including screening for autism spectrum disorders at age 16 and evaluations to confirm the diagnosis, using standardized measures, at age 21. Overall, 5 percent of the youths had autism spectrum disorder diagnoses, a rate described as five times that found in the general U.S. population. The lower the birth weight, the higher the likelihood of an autism diagnosis, with a 10.6 percent prevalence among those who weighed 3.3 pounds at birth and a 3.7 percent prevalence at 4.4 pounds.