# Personality disorder diagnoses in UK Autistic people: Evidence from a matched cohort study

## TL;DR

Autistic people in the UK are significantly more likely to be diagnosed with personality disorders than non-Autistic people, with a notable increase in diagnoses over time.

## Contribution

This study provides empirical evidence of a strong association between autism and personality disorder diagnoses, particularly highlighting gender and intellectual disability differences.

## Key findings

- Autistic individuals without intellectual disability had 4.6 to 4.8 times higher rates of personality disorder diagnoses compared to non-Autistic individuals.
- For Autistic individuals with intellectual disability, women had an 8.3 times higher rate of personality disorder diagnoses compared to non-Autistic women.
- The rate of personality disorder diagnoses among Autistic people increased from 14.67 to 22.43 per 10,000 person-years between 2009 and 2019.

## Abstract

Clinical accounts and cohort studies suggest that Autistic people are disproportionately likely to be diagnosed with personality disorder. We conducted a cohort study of adults diagnosed Autistic drawn from the IQVIA Medical Research Database, with follow-up from 1 January 2000 to 16 January 2019. We included a comparison group without diagnosed autism, matched (1:10) by age, sex and primary care practice. We included 22,112 Autistic adults, of whom 6437 (29.1%) had a diagnosis of intellectual disability. Median age was 20.36 (interquartile range: 18.0–28.5), and 16,881 (76.3%) were men. The rate of new personality disorder diagnosis in Autistic people without intellectual disability was 4.8 (3.5–6.7) times higher for Autistic versus comparison men, and 4.6 (3.1–6.8) times higher for Autistic versus comparison women. For Autistic participants with intellectual disability, the rate was 2.0 (1.0–3.7) times higher for Autistic versus comparison men and 8.3 (4.0–17.2) times higher for Autistic versus comparison women. The estimated rate of new personality disorder diagnosis for Autistic people aged 20 increased from 14.67 (95% confidence interval: 10.4–20.8) per 10,000 person-years in 2009 to 22.43 (95% confidence interval: 13.9–36.3) in 2019. The findings indicate that personality disorder diagnoses are more common in Autistic people and increased overall in women from 2000 to 2019.

Several research studies have suggested that Autistic people are more likely to be diagnosed with personality disorder than people who are not Autistic. We compared rates of personality disorder diagnoses between Autistic people and a comparison group of people not diagnosed Autistic using anonymised data collected by UK primary care practitioners for participants registered at a primary care (general practitioner) practice sometime between 1 January 2000 to 16 January 2019. The comparison group of people in the community who did not have an autism diagnosis were of the same age, sex and registered at the same primary care practice as their matched Autistic participant, with 10 times as many matched participants as Autistic participants. We included 22,112 Autistic adults, of whom 6437 (29.1%) had a diagnosis of intellectual disability. Median age was 20.36 years, and most, 16,881 (76.3%), were men. We included 221,120 comparison adults. New personality disorder diagnoses were more than four times as common for Autistic men and women without an intellectual disability compared to men and women in the comparison group. For Autistic participants with an intellectual disability, the rate was twice as high for Autistic versus comparison men and 8 times higher for Autistic versus comparison women. Between 2000 and 2019, there was an increase in the rate of new personality disorder diagnoses among Autistic people, and in women. The findings highlight the need for further investigation into reasons for this increase.