The researchers found intestinal inflammation in 6% of the 199 patients. The report said, " Lactose inflammation or injury may contribute to abdominal discomfort, pain and observed aberrant behavior....most not identified by clinical history."
This number is higher (65%) in children over the age of 5. Boys are at 1.7 times greater risk than girls.
Kushak, R. I., Lauwers, G. Y., Winter, H. S., & Buie, T. M. (2011). Intestinal disaccharidase activity in patients with autism: Effect of age, gender and intestinal inflammation. Autism, 3: pp. 285-294.