The 2nd to 4th digit ratio and autism

It has been suggested that autism may arise as the result of exposure to hi gh concentrations of prenatal testosterone. There is evidence that the rati o of the lengths of the and and 4th digit (2D:4D) may be negatively correla ted with prenatal testosterone. We measured 2D:4D in 95 families recruited via the National Autistic Society, UK. The sample comprised a total 72 chil dren with autism (62 males, 10 females; age range 2 to 14 years), including 23 children (20 males, three females) with Asperger syndrome(AS), 34 sibli ngs, 88 fathers, 88 mothers and sex- and age-matched control participants. We found that the 2D:4D ratios of children with autism, their siblings, fat hers and mothers were lower than population normative values. Children with AS, who share the social and communicative symptoms of autism but have nor mal or even high IQ, had higher 2D:4D ratios than children with autism but lower ratios than population normative values. There were positive associat ions between 2D:4D ratios of children with autism and the ratios of their r elatives. Children with autism had lower than expected 2D:4D ratios and chi ldren with AS higher ratios than expected in relation to their fathers' 2D: 4D ratio. It was concluded that 2D:4D ratio may be a possible marker for au tism which could implicate prenatal testosterone in its aetiology.