Could transgender men and women carry genetic variants that influence their gender identity? A biological basis for gender dysphoria may have been identified in a panel of genes, including the DNA involved in the development of nerve cells and the manufacture of sex hormones.

The findings support the claim that transgender people have fundamental differences in their brains and biochemistry that may help to explain why they feel their birth sex isn’t the correct one. Trans rights campaigners have long argued that being transgender is not a lifestyle choice but stems from a deep-rooted conflict between mind and body.

The scientists from Augusta University in Georgia undertook DNA testing of 14 female-to-male and 16 male-to-female transgender people and looked for genetic variants that were common in these groups. They found 30 such variants, 9 of which were in genes known to be implicated in the growth of brain cells or the production of sex hormones such as oestrogen and testosterone. The study, which was presented this month at a meeting of the Society for Reproductive Investigation in San Diego, California, has yet to go through peer review. It also involved a relatively small number of subjects. However, its preliminary results tally with other research that suggests there is something distinctive about the neurobiology of transgender people.

In the UK, there are thought to be between 300,000 and 500,000 trans men and women, a very small minority of whom have undergone gender reassignment surgery.

Bernard Reed, a founder and trustee of the Gender Identity Research and Education Society, said: “There is a growing amount of scientific evidence that, within the brain, there is a biological basis for these unusual gender identities, just as there is for being right or left-handed. Already, this has led to acceptance within the World Health Organisation and NHS England that the development of an unusual gender identity is not a mental illness.”