Abnormal brain growth and function are features of autism, an increasingly common developmental disorder that now affects 1 in 60 boys in the US. Now researchers from the University of Pittsburgh and Thoughtful House Center for Children in Austin, Texas, have found remarkably similar brain changes to those seen in autism in infant monkeys receiving the vaccine schedule used in the 1990’s that contained the mercury-based preservative thimerosal.
Throughout the study period, vaccinated animals showed an increase in total brain volume – a feature of the brain in many young children with autism - when compared with unvaccinated animals. However, a specific part of the brain associated with emotional responses that is thought to be important in autism, the amygdala, did not show abnormalities until after the 12-month vaccines had been given. In addition, after the 12-month vaccines only, the functional brain scans showed significant differences between vaccinated and unvaccinated groups. These functional scans looked at the activity of receptors for morphine-like compounds (opioids) that may play a role in the brain of children affected by autism. Vaccine administration was associated with an increase in opioid binding activity in the amygdala compared with a decrease in the unvaccinated group.