Introduction: There is growing clinical recognition that a significant proportion of people referred to gender identity clinics have co-occurrent autism spectrum disorder (ASD).
Aim: This master’s thesis aims to investigate the assumed co-occurrence between transgender identities and ASD by identifying studies investigating the prevalence of ASD in transgender populations and, vice versa, the prevalence of transgender identities in populations of people with ASD.
Method: To investigate this, a systematic literature review was conducted in order to provide an empirical overview of the current research on the topic. A systematic search was performed of PsycInfo, PubMed, Embase, Cinahl and Web of Science. The literature search was carried out using search terms related to ASD and transgender terms, including a) autism*, ASD, pervasive developmental disorder, PDD, autistic*, asperger* and b) gender nonconform*, gender non-conform*, gen- der variant*, gender incongru*, non-binar*, nonbinar*, transgender*, transsexual*, gender dysphor*.
Results: After applying in- and exclusion criteria, the final review yielded 25 studies that were relevant for the study objectives. Studies of both clinical and community samples were included. The prevalence of ASD in transgender populations varied from 0,69 % up to 26 %, while the prevalence of transgender identities was reported in up to 21,5 % of people with ASD.
Discussion: The included studies indicate that there is an increased co-occurrence. However, there is a lack of studies of high methodical quality and therefore the findings of the included studies should be viewed cautiously. Various underlying hypotheses for the link between ASD and transgender identities were suggested but all of them lack specificity. An explanation for the increased co-occurrence is most likely
to be multifactorial. Most importantly, ASD should not be an exclusion criterion for receiving gender-affirming treatment. Further research should set out to investigate the development of gender identity in people with ASD in order to gain a better understanding of the co-occurrence. As it remains unclear whether available treatment outcomes in transgender individuals are generalizable to transgender populations with ASD, follow-up studies in these populations are also necessary in order to pro- vide evidence for optimal care for this population.
Conclusions: Although the included studies of this systematic review has limitations, an increasing amount of evidence suggests a co-occurrence between ASD and transgender identities.