The 2D:4D ratio and its relationship with other androgenisation parameters in parents of individuals with autism spectrum disorders

The 2D:4D ratio is the quotient between the index and ring fin-ger lengths and is a non-direct indicator of androgenisation. If prenatal tes-tosterone levels in the amniotic fluid are high then the probability increases of developing lower ratio values. It has been suggested that people with au-tism spectrum disorders (ASD) and their parents may have highly andro-genised brains, and for this reason the 2D:4D ratio is used as a marker of such idiosyncrasies. This study aims to analyse if parents of people with ASD differ from the general population in several parameters of andro-genisation related to the 2D:4D ratio. The sample was composed of 43 parents of offspring with ASD and 42 controls who had the 2D:4D ratio measured, answered several trait questionnaires, and had their testosterone and cortisol levels measured. Although there were no differences between groups in the 2D:4D ratio, the left hand of the ASD parents showed greater predictive ability to explain empathy and autism quotients, coopera-tive behaviour, and cortisol levels. In addition, the severity of the symp-toms of their offspring was predicted only with male parents. The results indicate that the 2D:4D ratio could be used together with other parameters as an indicator of the likelihood of developing autistic traits in offspring.