Transgender adults are up to six times more likely to be diagnosed as autistic than those whose gender identity corresponds with their birth sex, researchers claim.
University of Cambridge analysed data from 600,000 adults drawn from five different datasets, including over 500,000 individuals questioned as part of the Channel 4 documentary 'Are you autistic?' which aired in 2018.
They found that rates of autism among transgender adults far surpassed the numbers for the British population as a whole.
While just over 1 per cent of the UK population is estimated to be on the autistic spectrum, up to 6.5 per cent of gender-diverse adults are on the autistic spectrum.
Transgender and gender-diverse individuals were also more likely to indicate that they had received diagnoses of mental health conditions, particularly depression.
A better understanding of gender diversity in autistic individuals will help provide better access to health care and post-diagnostic support, the experts say.
'This finding, using large datasets, confirms that the co-occurrence between being autistic and being transgender and gender-diverse is robust,' said study lead author Dr Varun Warrier at the University of Cambridge.
'We now need to understand the significance of this co-occurrence, and identify and address the factors that contribute to well-being of this group of people.'
Gender-diverse is the umbrella term used to describe those whose gender identity or gender role does not correspond to the sex assigned to them at birth.
For example, 'agender' describes someone who does not identify as having a gender identity, while 'two spirit' refers to someone who identifies as having both a masculine and a feminine spirit.
Cisgender describes a person whose gender identity corresponds with their birth sex.
While several studies have investigated rates of autism in cisgender individuals, there is limited information on rates of autism in transgender and gender-diverse individuals in the general population, the Cambridge team say.
Individuals who took part in the Channel 4 documentary provided information about their gender identity and if they received a diagnosis of autism or other psychiatric conditions such as depression or schizophrenia.
Participants also completed a measure of autistic traits, which included difficulty with social interaction and resistance to changing routines.
Across all five datasets, transgender and gender-diverse adult individuals were between three and six times more likely to indicate that they were diagnosed as autistic.
This was compared to people whose gender identity corresponds to their sex at birth, commonly known as 'cisgender'.
While the study used data from adults who indicated that they had received an autism diagnosis, it is likely that many individuals on the autistic spectrum may be undiagnosed.
As around 1.1 per cent of the UK population is estimated to be on the autistic spectrum, this result would suggest that somewhere between 3.5 per cent and 6.5 per cent of transgender and gender-diverse adults are on the autistic spectrum.
'Understanding how autism manifests in transgender and gender-diverse people will enrich our knowledge about autism in relation to gender and sex,' said Dr Meng-Chuan Lai, a collaborator on the study at the University of Toronto.
'This enables clinicians to better recognise autism and provide personalised support and health care.'
On average, transgender and gender diverse people scored higher on measures of autistic traits, regardless of whether they had an autism diagnosis.
They were also more than twice as likely as to have experienced depression.
The study did not investigate whether gender identity causes autism or the other way round, however.
'Both autistic individuals and transgender and gender-diverse individuals are marginalized and experience multiple vulnerabilities,' said Professor Simon Baron-Cohen, director of the Autism Research Centre at Cambridge.
'It is important that we safe-guard the rights of these individuals to be themselves, receive the requisite support, and enjoy equality and celebration of their differences, free of societal stigma or discrimination.'
The study has been published in Nature Communications.
© Associated Newspapers Ltd.