The results were drawn from part a cohort of all children born in Denmark between 1994 and 2003. During the study, over 340,000 boys were followed up to the age of nine between 1994 and 2013 and almost 5,000 cases of ASD were diagnosed. They found that regardless of cultural background circumcised boys may run a greater risk of developing ASD. The researchers also made the observation of an increased risk of hyperactivity disorder among circumcised boys in non-Muslim families. Risk was particularly high for infantile autism before the age of five, at least in epidemiology.
Lead author professor Morten Frisch of the Statens Serum Institut, Copenhagen, said, "Our investigation was prompted by the combination of recent animal findings linking a single painful injury to lifelong deficits in stress response and a study showing a strong, positive correlation between a country's neonatal male circumcision rate and its prevalence of ASD in boys."
Frisch says that today it is considered unacceptable practice to circumcise boys without proper pain relief but none of the most common interventions used to reduce circumcision pain completely eliminates it and some boys will endure strongly painful circumcisions. The researchers say that the pain associated with circumcision in very young babies is likely to be more severe during the operation and post-operatively. They cite papers claiming painful experiences in neonates in animal studies that were then associated with long-term alterations in pain perception, a characteristic often encountered among children with ASD.
"Possible mechanisms linking early life pain and stress to an increased risk of neurodevelopmental, behavioural or psychological problems in later life remain incompletely conceptualized," said Professor Frisch. "Given the widespread practice of non-therapeutic circumcision in infancy and childhood around the world, our findings should prompt other researchers to examine the possibility that circumcision trauma in infancy or early childhood might carry an increased risk of serious neurodevelopmental and psychological consequences."
Citation: Morten Frisch and Jacob Simonsen, Ritual circumcision and risk of autism spectrum disorder in 0- to 9-year-old boys - national cohort study in Denmark Journal of the Royal Society of Medicine DOI: 10.1177/0141076814565942