Hilary Cass evidence to MSPs on gender identity services

She added: "This may have been naive, but one of the things that I was surprised about in conducting this review is how much homophobia there still is as well as transphobia, so we do have to support people in being able to express and understand their sexuality as well as their gender identity."

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• ANALYSIS: The Cass Review, gender clinics, and a 'toxic' debate 
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Dr Cass, whose 388-page report published in April concluded that the evidence for prescribing puberty blockers and hormone treatments to under-18s with gender distress was "remarkably weak", said that it is unclear how many patients have gone on to de-transition in adulthood due to the lack of long-term follow-up studies and because individuals who regret it "don't necessarily come back to the NHS".

She said: "That is a significant problem, but I think it's more subtle than that because for example I spoke to a young adult who started to transition very early - male to female.

"She's doing well, she had puberty blockers at the earliest stage, she had feminising hormones at the earliest stage and she passes very well as a woman, but with hindsight she knows she was a boy with intense internalised homophobia and was gay.

"But at this point in her life she's clearly not going to de-transition."

The majority of referrals are for birth-registered females aged 12-17 (Image: Cass Review)

When the first NHS gender identity service was established at London's Tavistock clinic in 1989, it saw fewer than 10 children per year - mostly birth-registered males who identified as female.

Between 2018 and 2022, it was receiving thousands of referrals a year for under-18s, 73% of whom were birth-registered females.

The Sandyford clinic in Glasgow - Scotland's only NHS gender identity service for children and adolescents - has experienced a similar shift and surge in demand, with more than 1000 under-18s waiting for their first appointment with waiting times of over four years and a majority of the demand coming those seeking female-to-male transition.

The Cass Review said the 'toxicity' of debate had 'let down' children presenting with gender distress (Image: PA)

Dr Cass told MSPs that the changing profile of this cohort meant it was even harder to draw conclusions from existing evidence about the long-term consequences of puberty blockers.

She added that this group of young patients also had to be considered "within the broader context of what's happening to adolescence in Gen Z" - those born between the mid-1990s and the early 2010s.

Dr Cass said: "We know that there are very high rates of depression and anxiety, there are stresses that previous generations didn't have growing up in terms of social media, and expectations on young people that arise from that early exposure to pornography.

"We don't know what any of those do to how you might present your [gender] distress.

"Certainly for some young people, that distress or feeling that you don't fit what you perceive to be the expected gender norms may manifest through questioning your gender identity.

"That's why we have to take this as a new cohort and not rely on previous research, and work with young people to help them unpick all of those things that may have led to that gender distress."

The Sandyford clinic has suspended the prescription of puberty blockers and cross-sex hormones to any new patients under-18 following the publication of the Cass Review, but the restriction only applies to the NHS.

Dr Cass told MSPs that she had "really deep concerns" about private providers continuing to provide drugs off-label, and said that self-medication by young people was "happening way more than we would wish".

The Cass Review recommended a ban on puberty blockers to under-16s except within the context of clinical trials, and advised "extreme caution" in administering cross-sex hormones to 16 and 17-year-olds. 

A clinical trial into puberty blockers is currently under development in England, and is expected to incorporate sites in Scotland and internationally. 

There has been opposition from trans campaigners against restrictions on NHS medical treatment for under-18s (Image: PA)

Dr Cass told MSPs that the review's findings had been distorted by "significant misinformation", including the false claim that 98% of studies into puberty blockers and hormone treatments had been disregarded and only randomised control trials were included. 

"Both of those things are wrong," she said. 

Of the 102 research papers identified for puberty blockers and hormone treatments, none were randomised control trials but two were rated high quality and around 50 of moderate quality.

These were all included in the analysis. 

Weaknesses tended to include follow-up periods which were too short, patients dropping out over time, or inappropriate control groups, said Dr Cass. 

"It was a very poor literature compared to most other literature, including in children's healthcare practice, so that was quite striking," she said. 

Dr Cass stressed that medical transition was "a really important option" for youngsters whose trans identity would be long-term and enduring, but the difficult is correctly distinguishing those individuals from patients whose distress is rooted in other factors such as unhappiness with their sexuality, undiagnosed neurodiversity, family breakdown, and mental health. 

She said: "Medical transition does not come without costs in terms of effects on sexual function, fertility, knowns and unknowns about long term bone health, the limitations of surgery...it's a high cost to pay if, in the longer term, you don't [have a stable trans identity]. 

"Picking that sweet point where you have a high level of certainty that you're giving the treatment to the right people is very important.

"And the group that we have least understanding about is the group that we are most commonly seeing now in clinic, which is birth-registered females who are presenting in adolescence for whom there may be a range of other factors driving their gender-related distress."