Gender, assigned sex at birth, and gender diversity: Windows into diagnostic timing disparities in autism

Later autism diagnosis is associated with increased mental health risks. Understanding disparities in diagnostic timing is important to reduce psychiatric burden for autistic people. One characteristic associated with later autism diagnosis is female sex assigned at birth. However, literature to date does not characterize, differentiate, or account for gender identity beyond assigned sex at birth. Gender diversity may be more common in autistic relative to neurotypical people, and autism is proportionally overrepresented in gender-diverse populations. We examined age at autism diagnosis by assigned sex at birth, gender identity, and gender diversity (gender-diverse vs cisgender) status, separately. Three independent cohorts representing different ascertainments were examined: a research-recruited academic medical center sample (N = 193; 8.0-18.0 years); a clinic-based sample (N = 1550; 1.3-25.4 years); and a community-enriched sample (N = 244, 18.2-30.0 years). The clinic-based and community-enriched samples revealed disparities in diagnostic timing: people assigned female at birth, people of female gender, and gender-diverse people were diagnosed with autism significantly later than persons assigned male at birth, persons of male gender, and cisgender persons, respectively. Birth-sex, gender identity, and gender diversity may each uniquely relate to disparities in autism diagnostic timing. The influence of ascertainment strategies, particularly in studies examining assigned sex at birth or gender identity, should be considered.Lay Abstract Later autism diagnosis is associated with risk for mental health problems. Understanding factors related to later autism diagnosis may help reduce mental health risks for autistic people. One characteristic associated with later autism diagnosis is female sex. However, studies often do not distinguish sex assigned at birth and gender identity. Gender diversity may be more common in autistic relative to neurotypical people, and autism is more common in gender-diverse populations. We studied age at autism diagnosis by sex assigned at birth, gender identity, and gender diversity (gender-diverse vs cisgender) status, separately. We studied three separate autistic samples, each of which differed in how they were diagnosed and how they were recruited. The samples included 193 persons (8.0-18.0 years) from a research-recruited academic medical center sample; 1,550 people (1.3-25.4 years) from a clinic-based sample; and 244 people (18.2-30.0 years) from a community-enriched sample. We found significant differences in the clinic-based and community-enriched samples. People assigned female sex at birth were diagnosed with autism significantly later than people assigned male at birth. People of female gender were diagnosed significantly later than people of male gender. Gender-diverse people were diagnosed significantly later than cisgender people. Sex assigned at birth, gender identity, and gender diversity may each show unique relationships with age of autism diagnosis. Differences in how autistic people are diagnosed and recruited are important to consider in studies that examine sex assigned at birth or gender identity. More research into autism diagnosis in adulthood is needed.