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 finger lengths and is a non-direct indicator of androgenisation. If prenatal testosterone levels in the amniotic fluid are high then the probability increases of developing lower ratio values. It has been suggested that people with autism spectrum disorders (ASD) and their parents may have highly androgenised 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 androgenisation 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, cooperative behaviour, and cortisol levels. In addition, the severity of the symptoms 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.