Girls are protected from autism!

A team of Boston and European scientists have found evidence for a “female protective effect” in autism that could explain why boys are at far greater risk for the disorder than girls.

Autism is a spectrum of conditions, involving three broad characteristics: impairments in social interaction; impairments in communication; and restricted interests and repetitive behaviour. The genetics behind autism are complex and poorly understood. Whether genetic mutations or the inheritance of certain genetic traits are responsible for autism is controversial, but inheritance is certainly a risk factor. Psychologist Simon Baron-Cohen thinks scientists and engineers could be more likely to have a child with autism, because the parents pass on their traits for ‘systematising’ behaviour.

It has long been observed that boys are at higher risk for autism, 4 times that of girls. The female protective effect hypothesis suggests that boys manifest autistic behaviours more readily, whereas girls require a higher ‘etiologic load’: females exposed to the same risk factors exhibit less severe autistic traits than equivalent males. If this hypothesis is true, of sibling babies that are exposed to the same inherited risk factors for autism, or ‘familial etiologic load’, brothers would manifest autistic behaviour more often than sisters.

To investigate this, scientists working in Boston, London and Stockholm collaborated to study thousands of pairs of fraternal twins: pairs of siblings that had the same risk factors in their family. The study, published in PNAS, supports the female protective effect hypothesis. There is an as yet unknown component of female sex that protects girls from developing autism.

The results have implications for continued research into finding the genes responsible for autism, because it means the investigations should be controlled for gender. If the female protective effect could be elucidated, it potentially offers a cure or preventative treatment for boys.