The publication a few days ago of the Cass Review was anomaly in an otherwise toxic and polarised debate.

In contrast to the febrile culture war raging on and off-line, here was a calm, rigorous, and objective analysis of the evidence - or lack thereof - for prescribing puberty blockers and hormone treatments to gender-questioning children and teenagers.

Inevitably, its findings have been seized on for ideological point-scoring, but ultimately the report should be welcomed as a positive watershed in the long-running controversy - something which signals a better route forward, away from ad-hoc and potentially harmful practices towards more holistic approaches and greater scientific clarity.


Exactly how easy that will be to deliver is another matter, of course.

Dr Hilary Cass, the review's chair, recommends that under-18s experiencing gender distress should have access to a wide range of healthcare professionals to evaluate mental health issues or undiagnosed neurodiversity instead of being automatically referred to gender clinics operating in silo from other NHS paediatric services.

But child and adolescent mental health service (CAMHS) waiting lists are already huge, and referrals for suspected cases of autism and ADHD are also soaring.

The Cass Review also advises "extreme caution" in prescribing puberty blockers and cross-sex hormones to under-18s due to the lack of long-term evidence for their effects.

NHS England has already banned the use of puberty blockers in paediatric gender treatment outwith randomised clinical trials - except that no such trials are currently up and running (they are in the pipeline, however, with an expectation that Scottish patients will be able to participate).

It must be said that the number of under-18s prescribed puberty blockers on the NHS to delay normal puberty onset remains low: fewer than 100 in England, and maybe a tenth of that in Scotland.

Yet the demand for services has increased sharply, with more than 1000 children and adolescents on the waiting list for a first appointment at the Sandyford in Glasgow - Scotland's only paediatric gender clinic - as of February this year.

The average waiting time is four years.

The Herald: Scotland's only gender clinic for children and young people is based at the Sandyford in GlasgowScotland's only gender clinic for children and young people is based at the Sandyford in Glasgow (Image: PA)

It was against this backdrop, of growing waiting lists and concerns raised by whistleblowers that young people were being put at risk by the gender-affirming ethos at London's now-disbanded Tavistock clinic, that Dr Cass was commissioned back in 2020 to evaluate the quality of existing evidence.

The short answer? It's weak.

Only one of the 50 available studies on the use of puberty blockers in gender-questioning teenagers was deemed "high quality".

Likewise, only one out of 53 on the use of hormones was rated good.

There was "little or inconsistent" evidence for the effects of hormones on outcomes such as cognitive development, body satisfaction, fertility, bone health, and cardiometabolic effects - in other words, we're not sure whether they have an adverse effect or not.

Most of the studies on puberty blockers suggested treatment might affect height and bone health, but given that the research itself is weak there is no definitive answer either way.

Some recent early data has also suggested that their effects on testes and sperm may be irreversible, but again this is not yet peer-reviewed or published.

Dr Cass noted that there is "no evidence that gender affirming treatment in its broadest sense, reduces suicide risk" or that using puberty blockers to buy gender-conflicted youngsters "time to think" improves their psychological wellbeing.

The Herald: Dr Hilary Cass said the current evidence base for medical interventions in under-18s is 'remarkably weak'Dr Hilary Cass said the current evidence base for medical interventions in under-18s is 'remarkably weak' (Image: PA)

The bottom line for Dr Cass is that medical practice "did deviate from the clinical evidence", largely because it was based on international guidelines which were themselves grounded on flimsy studies.

What is urgently required is the same calm, rigorous, and objective ethos behind the Cass Review to be deployed into work on large, randomised control trials - the gold-standard for scientific research. 

This is the only credible way to determine whether under-18s can ever be offered these interventions safely, under what circumstances are they beneficial, and when might they do more harm than good.

At the moment, much of the discourse splits anecdotally between trans people who offer up first-hand experiences of the life-changing benefits of puberty blockers and hormones in easing their transition, and those who are scarred by a medical intervention which was wrong for them in long-run.

But medicine - especially when the NHS is picking up the tab - should be based on evidence, not anecdote.

The dilemma was summed up in a recent Private Eye podcast by Dr Phil Hammond, the magazine's 'MD' health writer and a retired GP who worked in paediatric ME.

He said young patients uncomfortable with their gender should be "as gender-fluid as you like for as long as you like", but take care before "outsourcing" their gender identity to pharmaceutical industry or surgeons.

He added: "Occasionally you would meet someone who had had a lot of interventions, and treatment, and surgery and they'd be absolutely delighted.

"And occasionally you would meet someone who deeply regretted it.

"The issue then becomes: how do you have enough time and therapy and understanding in an overloaded clinic, with so many people, to explore the issues and try to spot the people who will benefit from the people who won't benefit?"

The Herald: Trans issues have been propelled into the spotlight in Scotland by Scottish Government-led attempts to bring in new gender recognition lawsTrans issues have been propelled into the spotlight in Scotland by Scottish Government-led attempts to bring in new gender recognition laws (Image: PA)

Transgender medicine is not necessarily unique in resting on shaky foundations.

Dr Rona Carroll, a New Zealand-based GP specialising in transgender healthcare, noted that the "majority of evidence presented in most medical guidelines would not be classed as high quality".

Long-term use of antidepressants has become a norm, for example, yet few clinical trials on their effects extend beyond 12 weeks.

Nonetheless, the Cass Review has increased pressure on NHS Scotland to ban the use of puberty blockers for paediatric gender dysphoria.

David Bell, a senior psychiatrist and Tavistock whistleblower, has also called for the Sandyford clinic to close because its model of care - affirming the child's gender identity and adopting a medical pathway - is based on the same "weak" guidelines used by Tavistock.

"One of the things Cass points out is that the ordinary canons of clinical judgment have been overtaken by gender ideology and this is continuing in Scotland," he said.

The Cass Review has underlined an absence of evidence. The next step must be to correct that, with robust trials and a willingness by all sides to accept the findings - regardless of ideology.