City Research Online

Abstract

An increasing number of adults have been receiving an autism diagnosis in recent years, due to changes in diagnostic criteria and increased awareness. It is unclear whether certain groups are more likely to face disparities when seeking a diagnostic assessment. As diagnostic criteria and tools are shaped by research, research samples should reflect the diversity of the autistic population.

This systematic review examined the demographics of adult-diagnosed autistic people represented in quantitative research. We searched Web of Science, PsycINFO, Embase, Medline, and ProQuest Dissertations & Theses for eligible studies and conducted citation searching, identifying 108 eligible studies. We used a random-effects proportional meta-analysis to estimate the pooled proportions of participants reported as female, women-identifying participants, gender-diverse, and ethnically and racially minoritised participants, and participants with ten common co-occurring psychiatric diagnoses, i.e. anxiety, depression, ADHD, OCD, intellectual disability, bipolar disorder, psychotic disorders, substance use disorders, and personality disorders.

The pooled proportion of participants reported as female was 35.51%. Only five studies reported on gender-diverse participants, who comprised an estimated 10.50%. Twelve studies included data on race/ethnicity with a pooled proportion of ethnically and racially minoritised participants of 10.45%. The pooled proportions of participants with co-occurring conditions ranged from 5.94% for substance use disorders to 33.56% for depression.

We identified high heterogeneity levels and gaps in demographic reporting across studies, especially regarding gender identity, race/ethnicity, and intellectual disability. We discuss the implications of these gaps in representation and reporting and differences between sample sources for the generalisability of research findings people.

Publication Type:	Article
Additional Information:	© 2026, the authors. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)
Publisher Keywords:	adult diagnosis; representation; equity; gender; ethnicity; mental health
Subjects:	B Philosophy. Psychology. Religion > BF Psychology H Social Sciences > HN Social history and conditions. Social problems. Social reform R Medicine > RC Internal medicine
Departments:	School of Health & Medical Sciences School of Health & Medical Sciences > Department of Nursing & Midwifery
SWORD Depositor:	Symplectic Administrator

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