Female-to-male transsexuals and autistic traits

Background: Females with autism spectrum conditions (ASC) are hyper-masculinized in specific aspects of their behaviour and cognition. Objectives: Here we test the prediction that those females with extreme Gender Identity Disorder (GID) who opt for gender reassignment and who can therefore be assumed to be masculinized will have elevated AQ scores. Methods: 5 groups were compared: (1) female-to-male (FM) transsexuals (n = 61); (2) male-to-female (MF) transsexuals (n = 198); (3) typical males (n = 76); (4) typical females (n = 98), and (5) individuals with Asperger Syndrome (AS) (n = 125). All participants completed an online version of the AQ. Results: The FM transsexuals' mean AQ score (x = 23.3, sd = 9.1) was significantly higher than both typical females (biological sex-matched controls) (x = 15.4, sd = 5.7), typical males (gender-identity matched controls) (x = 17.8, sd = 6.8) and MF transsexuals (16.6, sd = 6.9), but significantly lower than individuals with AS (x = 36.7, sd = 8.0). Approximately 30% of the FM transsexuals had an AQ in the Medium (MAP (AQ = 29-34)) or Narrow Autism Phenotype (NAP (AQ = 35+)) range. FM transsexuals had a 14-fold increase in the rate of NAP relative to typical males. Conclusions: These results confirm that those females with GID who opt for gender reassignment have a higher number of autistic traits. We speculate that these biological females, being masculinized in their autistic traits, may have had difficulties socializing with a female peer group and therefore found it easier to identify with a male peer group. This research illustrates how carefully selected groups in the population (e.g., congenital adrenal hyperplasia) can inform the extreme male brain (EMB) theory of autism.