Weighing the causes of autism

While researchers increasingly focus their efforts on the genetic underpinnings of autism spectrum disorder (ASD), there s no denying that its causes most likely involve a variety of factors. To that end, a team led by a Northwestern University researcher studied the relationship between ASD and low birth-weight and they found a positive correlation.

Dr. Molly Losh, who specializes in communications sciences related to neurodevelopmental conditions, led the study. She and her colleagues examined data from 3,715 pairs of same-sex twins, both fraternal and identical, born between 1992 and 1995 in Sweden. One member of each pair of twins had ASD, and Dr. Losh found that the twin with ASD was significantly more likely to have a low birth weight. In fact, a weight difference of at least 15 percent, or 400 grams, made the smaller twin three times as likely to develop ASD. The findings support the theory that, while certain genes may make a person susceptible to ASD, non-genetic factors, like low birth-weight, may increase that susceptibility.

ACSH s Dr. Gilbert Ross is intrigued by results of the study, and wonders whether a broader analysis of the incidence of low birth weight and autism, not necessarily involving twins, would yield further support for Dr. Losh s findings.