An Open Letter from Genspect to Dr Hilary Cass

Regarding the proposed NHS puberty blocker trial

Dear Dr Cass

We offer our sincere thanks for your scholarship, your integrity, and the clarity of thought embodied in the Cass Review. Your work marked a decisive line in the sand. We now speak of a post-Cass landscape because you helped the world recognise that something had gone seriously wrong in the treatment of distressed young people. For this we remain deeply grateful.

It is in this spirit of respect that we write to you regarding the proposed NHS puberty blocker trial. This trial is unethical in principle and unsafe in practice. The multiple foundational flaws in the PATHWAYS study design, along with the conceptual errors on which the entire protocol rests, have already been well documented.

More importantly, the very notion of a trial designed to test whether it is appropriate to block a child’s development toward healthy adulthood is conceptually flawed. To accept the validity of such a trial is to accept the existence of the transgender child. This is exactly what Harriet Hall described as Tooth Fairy Science, where researchers gather data without ever asking whether the phenomenon under investigation exists at all. The PATHWAYS trial administers a potent endocrine disruptor to healthy adolescents on the basis of a condition that is experienced in the mind rather than rooted in the body. No amount of survey data or bone density measurements can salvage a study whose premise was mistaken from the outset.

The entire trial is fruit from a poisoned tree because its foundational premise is false. If the diagnosis itself is a fiction, then every data point derived from it is contaminated. No methodological rigor can redeem research that begins with a mistaken assumption.

The PATHWAYS trial will not “put the issue to bed by establishing whether the drugs are effective,” despite your recent comments in the Sunday Times. We already know that the drugs are effective. Puberty blockers halt the natural process of sexual maturation in adolescence. They stop children from developing into healthy adults. These drugs reliably block puberty, prevent the awakening of reproductive systems, impede the development of sexual function, compromise future fertility, and impair a young person’s capacity to pair bond, to fall in love, and to mature into healthy adulthood. No trial is needed to confirm any of this. We already know this.

The two-year follow-up period cannot capture the long-term consequences, because the very nature of the intervention ensures that the damage unfolds only in adulthood. Short-term satisfaction cannot be allowed to eclipse the well-documented long-term harms. This is precisely why medicine cannot be demand led. Medicine must be guided by first principles that protect the young and the vulnerable from making decisions they cannot possibly comprehend.

The entire field of “gender medicine” is still searching for a cautious route along the same misguided path rather than finding the courage to acknowledge that we took the wrong road. We cannot medicalise identity; an individual’s identity is forged through life’s experiences, not through pills.

Many people view extremely gender nonconforming children as a transgender child. (I once was one of those children.) Yet the intensity of conviction often seen in children like this is matched only by the immaturity that leaves them prone to magical thinking. The long-term consequences are entirely incomprehensible to a pubescent child. They cannot meaningfully grasp the reality of lifelong infertility or impaired sexual functioning. They cannot understand what it means to reach adulthood unable to experience romantic attachment in a healthy and fulfilling way. These are adult challenges and adult losses.

This is why we created the Memorandum of Understanding on the Role of Puberty in Adolescence. Puberty is not an optional stage of life. It is the only gateway to healthy adulthood and it must be protected. Children deserve compassionate psychological care as well as the right to an open future whenever possible. You will also find attached Genspect’s briefing on detransition and puberty blockers, in which detransitioners reflect on what they would like to say to young people considering medical transition. Their experiences have so much to teach us about how to prevent further harm.

We urge you, with the respect your work commands, to reconsider support for this trial. Putting children into an experiment that suppresses their development, based on a trial that is designed around short-term outcomes, cannot meet ethical standards in any era, least of all post-Cass.

Thank you once again for all you have done to realign this field with evidence, reality, and safeguarding. We now have an opportunity to complete that realignment and protect children from further harm.

With sincere respect,

Stella O’Malley

Director and Founder, Genspect