Autism symptoms in relation to gender diversity: comparisons between a general population sample and a clinical sample

Gender is a multi-dimensional concept, and it is defined as the attitudes, feelings, and behaviors that culture associates with a person’s sex assigned at birth (1,2). Gender identity (or felt gender) denotes an individual's subjective sense of self as woman, man, or other non-binary gender, that may or may not align with their sex assigned at birth (2,3). Gender expression is illustrated through appearance and mannerisms, which might be gender-conforming or not (3,4). Gender contentedness is a measure of one’s happiness with being the gender aligned with sex (3,4). Gender Incongruence (GI), in the 11th edition of the International Statistical Classification of Diseases (ICD-11), is defined as a condition in which an individual's gender identity does not align with their sex assigned at birth (5). An individual with GI may or may not experience distress and impairment caused by incongruence (5). In DSM-5, the concept of Gender Dysphoria (GD) is in turn defined by the presence of significant distress and impairment in functioning that may accompany gender incongruence for a period of at least six months, which indicates that not all transgender and gender diverse (TGD) individuals will necessarily experience GD (5,6). The ICD-11 reformulated the previous ICD-10 term “Transsexualism” to “Gender Incongruence of adolescence and adulthood” and “Gender Incongruence of childhood” (5). The concept of GI was relocated from the "Mental and Behavioral Disorders" to "Conditions Related to Sexual Health" chapter. This illustrates the current understanding that TGD identities are not indicative of mental illness, and that categorizing them as such may result in significant stigma, both for the individual and within the broader community (5,6). GI frequently gives rise to seeking of gender-affirmative healthcare (GAH), with the objective of aligning the body's sex characteristics with the experienced gender (6,7). GAH may be provided through a single or a combination of medical interventions, including feminizing or masculinizing hormonal treatment, surgery, and/or psychosocial support (6,7). Autism spectrum disorder (ASD) is a neurodevelopmental condition characterized by persistent impairment in reciprocal social communication and social interaction, alongside restricted, repetitive patterns of behavior, interests, or activities, which emerge during early childhood and significantly limit or impair an individual’s functioning (8). Only individuals who have severe impairments in daily life warrant a clinical diagnosis, which is estimated as around 0.6-2% of the general population (8,9). The presentation of ASD symptoms (referred to as ASD traits in some studies) varies within the general population, with diagnosed individuals occupying the upper end of the distribution and neurotypical individuals demonstrating some symptoms, which underscores the necessity of a spectrum approach to understanding and addressing ASD symptoms (10–13). ASD and ASD symptoms are highly prevalent in TGD individuals (14–17). In a large study involving 292,000 participants aged 2-18 years, individuals diagnosed with ASD were observed to have a four times higher prevalence of GD compared with matched control individuals (18). Another recent study demonstrated that children with ASD diagnoses exhibited higher levels of gender incongruence in The Gender Diversity Screening Questionnaire self-report and parent-report measures when compared to typically developing children (19). It has been observed that ASD symptoms and gender diversity manifestation often occur in conjunction, but their interrelations have been predominantly investigated in clinical samples (20,21). In contrast, a recent study used five distinct datasets derived from the general population (14). It was found that TGD individuals, after controlling for age and educational attainment, were 3.03-6.36 times more likely to have an ASD diagnosis than were cisgender individuals (whose gender identity matches their sex assigned at birth). Additionally, TGD individuals scored significantly higher on self-report measures of ASD symptoms (14). A synthesis of 11 studies examining the interrelationship between ASD symptoms and GI was recently conducted through a systematic review and meta-analysis (16). Quantitative studies of adult, adolescent and child populations were included. The study indicated that the mean difference in the number of reported ASD symptoms between GI and population-based control participants was moderate, with a Hedges' g value of 0.67 (16). A potential limitation of these studies is that in all datasets gender identity was assessed using pre-defined categories (e.g., female, male, transgender), which may result in the underrepresentation of individuals identifying as another gender due to the absence of an open answer option to describe their experienced gender. A further consideration is that ASD symptoms were assessed primarily through the Autism Spectrum Quotient-50 (AQ-50) and the shorter version, AQ-10. These instruments were developed based on clinical experience of problems of people with Asperger Syndrome (13). The AQ-50 and AQ-10 do not differentiate between subcategories and may demonstrate low discriminant validity in scores between individuals with mild ASD and controls, which constrains their utility in assessing more subtle ASD symptoms (10,22). Finally, in both studies there was no information about differences between clinically referred TGD individuals and general population samples regarding the manifestation of ASD symptoms. The existing research on the co-occurrence of ASD and GI/GD has been conducted primarily in clinical samples of individuals seeking transgender healthcare. A limited number of studies have included samples from the general population. The relationship between ASD symptoms and gender diversity remains poorly understood, primarily due to the lack of comprehensive assessment of gender in the majority of studies. The aforementioned arguments indicate a need for further research to assess the intersection of ASD and GI with more detailed and, in the case of gender identity, dimensional measurement instruments. This may allow for the identification of milder ASD symptoms and facilitate a less categorical approach to understanding gender diversity.