Circumcision before the age of five can double a boy’s risk of developing autism, controversial research suggests.
Scientists believe the finding may be linked to stress caused by the pain of the procedure.
The study of more than 340,000 boys in Denmark found that circumcision raised the overall chances of an autism spectrum disorder (ASD) before the age of 10 by 46%.
But if circumcision took place before the age of five it doubled the risk.
Circumcision also appeared to increase the likelihood of boys from non-Muslim families developing hyperactivity disorder.
Professor Morten Frisch, of the Statens Serum Institut, Copenhagen, who led the research, 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.”
While it is considered unacceptable today to circumcise boys without proper pain relief, it is not possible to make the procedure completely pain-free.
The pain of circumcision is likely to be more severe in very young babies both during and after the operation, according to the scientists.
Painful experiences in newborns have been shown in both animal and human studies to be associated with long-term alterations in pain perception, a characteristic often seen in autistic children.
Prof Frisch added: “Possible mechanisms linking early life pain and stress to an increased risk of neurodevelopmental, behavioural or psychological problems in later life remain incompletely conceptualised.
“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.” …