July 28, 2006

Study debunks birth season-autism risk link

By Anne Harding

NEW YORK (Reuters Health) - One of the largest studies to
date to look at the issue has found no relationship between the
month a person was born and his or her risk of autism.

The risk of some psychiatric disorders, for example
schizophrenia, has indeed been linked to season of birth, Dr.
Abraham Reichenberg of the Mount Sinai School of Medicine in
New York City and colleagues note. But studies of autism and
birth month have had conflicting results.

It is not that just being born in a particular month that
could influence risk, Reichenberg noted in an interview with
Reuters Health. Instead, the season in which a person is born
reflects their exposure to certain types of infectious agents
in the womb. An example is whether their mother caught the flu
during flu season. Nutrition could also vary throughout the
year, he added.

Such exposures would not cause the disorder, he explained,
but might be interacting with genes or nutrition to affect
risk. "We don't really know how it works," he said.

Reichenberg and his team looked at Jewish men and women
born in Israel during the early 1980s who were assessed by the
Israeli Draft board at the age of 17. There was a total of
311,169 people, including 211 with autism or related disorders.

The researchers point out that a person with autism in the
group they evaluated would be likely to truly meet diagnostic
criteria for the condition, especially since the individuals in
the study grew up in an era where the diagnosis of autism was
much more rare than it is today.

The researchers found no link between the month a person
was born and autism risk. "In light of the present and other
recent findings, it would seem logical that future attempts to
identify an association between birth months and risk for
autistic spectrum disorders should be exercised with caution,"
they conclude.

SOURCE: American Journal of Psychiatry, July 2006.