The UK is Restarting a Puberty Blocker Trial Despite 25 Years of Evidence - Carrie Clark (#4)
13 March 2025
With Carrie Clark
UK
Carrie Clark of Genspect UK joins Stella O'Malley and Mia Hughes to examine the NHS Pathways study, a £10 million puberty blocker trial proceeding despite the Cass Review's damning assessment of the now-closed Tavistock clinic. The episode dissects the study's missing exclusion criteria, its continued reliance on self-reported data, and the NHS's refusal to follow up on 9,000 children already treated at GIDS. For Ireland, where HSE gender services have drawn on the same UK and Dutch frameworks now under scrutiny, the evidence gaps this episode identifies are directly relevant.
Carrie Clark, Director of Genspect UK, joins Stella O'Malley and Mia Hughes to scrutinise the NHS Pathways study, a £10 million puberty blocker trial announced in the aftermath of the Cass Review. That review exposed systemic failures at the Tavistock Gender Identity Development Service, which has since been closed. Clark's central argument is that the proposed new trial repeats the methodology of its predecessor rather than correcting it, offering the appearance of scientific rigour without the substance. Among the specific concerns raised in the episode is the study's apparent lack of meaningful exclusion criteria for young people with significant mental health difficulties or autism. Both conditions were heavily represented in the GIDS population, yet neither appears to function as a disqualifying factor in the new study's design. The episode also examines the continued reliance on self-reported outcome data, a methodological weakness that undermined earlier research in this field and that Clark argues the new study has not resolved. A figure that recurs throughout the conversation is 9,000: the approximate number of children who passed through GIDS before it closed. The NHS has not conducted systematic follow-up on these young people, meaning the health system is beginning a new research programme without knowing what its previous clinical model produced. Equally significant is the exclusion of detransitioners from the consultation process that shaped the Pathways study. People who have reversed gender transition represent a population whose experiences are directly relevant to any honest assessment of risk and outcome, and their absence from the process is treated here as a serious methodological and ethical failing. The episode also examines the scientific foundations on which puberty blocker use in adolescents has been built. The Dutch Protocol, developed in the 1990s, was the research that justified the practice internationally, but Clark identifies significant limitations in its methodology and the narrowness of the patient population it studied. Also discussed is an early intervention study conducted at Tavistock whose results were not given prominence, and a US study by researcher Joanna Olson-Kennedy whose findings remain unpublished. For those following developments in Ireland, this episode merits close attention. HSE gender services have been shaped by UK and Dutch clinical frameworks, and when those frameworks are subjected to serious methodological challenge, the questions do not stop at the Irish Sea. What evidence base underpins current HSE practice with gender-questioning young people? How are children with co-occurring mental health needs assessed before any medical pathway is considered? Are young people treated in Ireland being followed up in any systematic way? This conversation makes those questions harder to set aside. What Clark, O'Malley and Hughes argue throughout is that a publicly funded health system owes the children in its care evidence rather than ideology. The Cass Review created a moment of genuine accountability in the UK. Whether the Pathways study represents a real attempt to build on that accountability, or an effort to reinstate familiar conclusions under a more expensive methodology, is the question this episode examines with sustained and well-sourced rigour.
