Gender dysphoria could be triggered by childhood stress and potentially cured with medicine, a scientist has claimed.

Dysphoria is when someone feels their gender identity and their biological sex don't match and it may lead to them choosing to be transsexual.

Dr Stephen Gliske, a neurologist at the University of Michigan, disputes the widely-held theory dysphoria is caused by differences in physical brain sizes.

Instead, he claims the medically-recognised condition is caused by changes in brain activity which happen during someone's life.

And this, he said, means they could be 'resolved' without the person feeling the need to change sex or live as another gender – although he did not suggest how.

Critics have hit back at Dr Gliske's theory, branding it 'problematic' because it suggests dysphoria is something to be fixed like an illness.

A University of Michigan neurologist claimed gender dysphoria could be caused by changes in the activity in people's brains, rather than them developing in a different way (stock image of nerves in the brain)

One argued other people's attitudes were where change was needed, rather than the brains of people with gender dysphoria.

NHS treatment currently revolves around giving people psychotherapy or, in some cases, transition treatments like hormones or reassignment surgery.

But Dr Gliske said the current understanding of gender dysphoria is too 'inaccurate' to justify giving someone sex-change surgery.

Dr Gliske reviewed past papers published about dysphoria and published his theory in the medical journal eNeuro.

He said that, in the past, scientists have looked to size variations in areas of the brain to explain why someone may feel they have been assigned the wrong gender.

'The bed nucleus of the stria terminalis (BNST) was found to have a smaller average size in male-to-female (MtF) transgender individuals, with a size more similar to that of an average cisgender female than cisgender male,' he wrote.

Dr Gliske said brain imaging studies don't support the theory that gender dysphoria is caused by differences in the physical shapes of people's brains.

He wrote: '[My] theory proposes that gender dysphoria is not merely due to static changes in anatomy, as in the previous opposite brain sex theory, but instead includes dynamic activity on interacting, functional networks.

WHAT IS GENDER DYSPHORIA? Gender dysphoria is a condition in which someone becomes distressed because they don't feel that their biological sex matches the gender they identify as. For example, someone may feel like a woman and want to live as a woman, but have been born with the anatomy of a man. Gender dysphoria is a 'recognised medical condition, for which treatment is sometimes appropriate. It is not a mental illness,' according to the NHS. People who live as a gender which is not the same as their biological sex are called transgender. Some people may choose to have hormone therapy – for example, to make them grow hair or develop breasts – or to have reassignment surgery to give them the genitals of a person of the sex they identify as. People diagnosed with gender dysphoria are allowed to legally change their gender. According to the charity Stonewall, as many as one per cent of the population may be trans - although accurate numbers are not known. Advertisement

'Changes in sex hormones due to puberty (or aging) could also affect these identified networks, explaining both resolution without treatment in childhood onset causes and the possibility of late-onset cases.'

Dr Gliske's research lays out elements of a person's life which he said 'influence their sense of gender'.

These include the culture they live in, external feedback – so interactions with other people, levels of distress and their own perception of their body.

For example, he said a child predisposed towards gender dysphoria may develop it if they had a particularly stressful life.

Whereas in many with the same disposition it might be 'resolved' – the condition is estimated to disappear from as many as 80 per cent of pre-pubescent children who have it, the study said.

And he said that doctors should focus on tackling someone's mental or emotional symptoms instead of doing 'potentially irreversible' and 'invasive' reassignment surgery.

'Treatments based on our new theory could instead involve targeting the distress and/or body ownership networks,' Dr Gliske said.

He said that they could 'seek to restore a sense of ownership over body parts'.

Social work professor at Flinders University in Adelaide, Dr Damien Riggs, was not involved with the research but said it started from a place which assumed gender was something you could find in the brain.

'It is problematic as it treats gender dysphoria as a pathology to be fixed, despite evidence demonstrating that dysphoria is best addressed via affirming treatment,' Dr Riggs said.

Dr Gliske proposed a variety of things in someone's life, such as stress and culture, could push them towards developing gender dysphoria, and that it might not be unavoidable

'It is problematic as it treats gender dysphoria as synonymous with being transgender, when in fact not all people experience dysphoria.

'And it is problematic as it treats gender diversity itself as a problem, rather than attitudes towards transgender people as being the problem.'

Professor Catherina Becker, a brain expert at the University of Edinburgh, said: 'The author suggests changing current clinical practice and to base treatments for gender dysphoria on his theory instead.

'What these treatments should be remains unspecified and these recommendations should therefore be taken with caution.'

Professor Derek Hill, from University College London, said: 'There is a long standing theory that gender dysphoria is associated with underlying difference in the size of brain structures, based on experimental work done in the 1990s.'

He said Dr Gliske's work suggested this theory didn't have a very strong explanation, but that the neurologist's own theory 'must be considered speculative'.

He added: 'It is quite possible... that some of the associations suggested here by the authors between gender dysphoria and brain function are chance random findings – the underlying data the authors have looked at is very noisy so the assumptions that underpin their theory are all subject to uncertainty.'

Dr Riggs added: 'In sum, the claims presented by Gliske take a clinical diagnosis (‘gender dysphoria’) as a rationale for interpreting the lives of transgender people.

'This is in direct contradiction to the histories of the diagnosis itself, and to the lives of transgender people who, there is no reason to believe, come to understand their gender in any way different than do any group of people.'