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Doubt cast on Tavistock gender clinic's puberty blockers trial

Serious concerns have been raised about current treatment of gender dysphoric children – and they deserve our serious attention, writes STEPHANIE DAVIES-ARAI

LAST month the BBC’s Newsnight programme joined a growing media focus on the work of the Tavistock Gender Identity Development Service (GIDS), which is the only service for gender dysphoric children and adolescents in the UK.

Gender dysphoria is a condition where a person feels discomfort and unhappiness over their biological sex. 

The controversy the Newsnight report explored was in relation to the Tavistock’s early intervention study (or the puberty blockers trial as it’s known), which in a trial group reduced the age at which GIDS prescribed puberty blockers to treat dysphoria from age 16 to 12.

GIDS says that blockers can be used to create a “window” during which a gender dysphoric child can be permitted more time to consider whether they wish to move on to cross-sex hormones. 

The Newsnight report followed on from an investigation by Professor Michael Biggs of the department of sociology at Oxford, first published by Transgender Trend in March this year.

Biggs discovered two important results of the trial: 

1. That there was no significant psychological improvement which could be attributed solely to the use of blockers, and 

2. That after a year on blockers there was a significant increase in the rate of children experiencing thoughts of self-harm and suicide. 

Biggs’s research was only the latest question about a trial which has been characterised by obfuscation and contradictory information since it began. To understand the significance of the controversy and the importance of asking these questions it’s helpful to go back to the beginning. 

GIDS began its trial of puberty blockers in 2011. Up to that point, puberty blockers were only available to 16-year-olds who had shown persistence of gender dysphoria, normally since early childhood. 

Cross-sex hormones were only available at adult clinics. What GIDS wanted to do was lower the age to 12 for a carefully selected trial group, following the lead of some clinics abroad, even though the quality of evidence for the use of puberty blockers was internationally classified as “low.” 

The trial was to transform the nature of the service at GIDS completely, from an exploratory model into, effectively, a model of assessment towards a medical intervention pathway. Cross-sex hormones are now offered at GIDS at age 16. 

There have been completely unexpected changes in the cohort of referrals since the trial began which mean that, regarding treatment, there are now so many unknowns.

In 2009/10 there were 97 referrals to GIDS, the majority boys. In 2018/19 there were 2,590 referrals, 75 per cent girls. A new phenomenon, termed rapid onset gender dysphoria, had emerged where adolescents, mainly girls, developed gender dysphoria after puberty had started, with no previous indication in childhood. Some 35 per cent of referrals are autism spectrum adolescents. 

There is a high rate of pre-existing mental health problems, self-harm, trauma, sexual abuse and chaotic and troubled family lives. The influence of transgender activism has spread from Tumblr and YouTube into the classroom, where children are taught from the youngest age that they can choose to be a boy or a girl. 

A system of “self-ID” has increasingly become policy in the treatment of children, through schools and child and youth services and organisations.

The political and cultural landscape is unrecognisable compared to 2010 when GIDS first applied for ethical approval for its trial. 

But even back then the reason for the trial, and specifically the structure of the trial, was presented by GIDS as due to demand from parents and lobby groups such as Mermaids and GIRES. 

Normal medical trials involve a control group. Without a control group to compare, positive results cannot be attributed to the effects of the drug with any certainty. 

The GIDS puberty blockers trial was rejected by the first ethics review committee specifically because the proposal did not include a control group, but it was accepted unchanged by a second ethics committee, raising questions about the robustness of the ethical review procedure. 

GIDS was following the pattern of previous studies in “transgender medicine” which do not follow normal medical standards; the GIDS trial would simply add yet another “low-quality evidence” study to the existing low-quality data base.

Not only was it a poorly constructed trial, but public comments from GIDS director Polly Carmichael suggest that conclusions were drawn and acted upon before the trial was even over. 

Although ethical approval was only given to lower the age to 12, at some point the NHS approved replacing the age restriction with the specification that a child must have reached what is known as the Tanner Stage 2 of puberty, so blockers could now be given to children as young as nine or 10, according to Carmichael in 2013.

In 2014 Carmichael stated in the Daily Mail: “Now we’ve done the study and the results thus far have been positive we’ve decided to continue with it.”

Yet in a recent statement on its website the Tavistock says that the trial only ended in February this year and that full results are now being drawn up for publication. 

Perhaps the most troubling example of the presumptive announcements of the safety of blockers was Carmichael’s contribution to the CBBC documentary I Am Leo, first broadcast in November 2014. 

Aimed at an audience of six to 12-year-olds, this film teaches children that some girls have “blue” brains rather than “pink” brains so they are really boys trapped in a female body. 

Carmichael, in her consulting room, reassures “Leo” that puberty blockers simply “pause” the body: “and the good thing about it is that if you stop the injections it’s like pressing a ‘start’ button and the body carries on developing as it would as if you hadn’t taken the injection.” 

There is simply not the robust evidence to support this assertion.

If recent changes in the cohort of referrals to GIDS were not anticipated (and are still not understood) there were some results from the trial which have added to the quality of the evidence base, by replicating the results of earlier studies. 

Back in 2012 the Tavistock was aware of two research studies which showed that 100 per cent of children on blockers progressed to cross-sex hormones, in the Netherlands (2011) and Australia (2012). 

In 2016, GIDS’s own results showed the same: evidence was emerging that “persistence was strongly correlated with the commencement of physical interventions such as the hypothalamic blocker […] and no patient desisted after having started on the hypothalamic blocker.” 

By comparison, of those children who did not start on the blocker, 90.3 per cent desisted. 

Are puberty blockers, then, simply a “pause button” to buy time or do they work to prevent the natural resolution of gender dysphoria during puberty, which was the case previously in over 80 per cent of gender dysphoric children? 

There is no diagnostic procedure which enables us to predict which children will persist and which will desist, so unless the GIDS team were 100 per cent accurate in their predictions — ie they selected only the children who would have persisted anyway to commence the blocker — false positives have been created. 

And as the commencement of blockers at Tanner Stage 2 followed by cross-sex hormones at age 16 results in sterility and compromised sexual function, this is not a result where we can just shrug our shoulders and say “oh well.” 

Throughout the duration of the GIDS trial, there has been more evidence emerging about the potentially harmful effects of blockers on the developing adolescent brain. 

People may be unaware of the fact that, uniquely in medicine, the use of puberty blockers for gender dysphoria (ie at the start of natural puberty) has been trialled on children before being tested on animals. 

In a presentation at the Tavistock conference The Science of Gender in 2018, Professor Neil Evans outlined early results of an ongoing trial on sheep which suggest that if a critical window of learning is missed, the effects will be permanent even if puberty blockers are subsequently stopped. 

Decreased stress response and deficit in long-term spatial memory are two examples of permanent negative effects of puberty blockers revealed by the sheep trials.

Prof Biggs has subsequently published a further report of his findings which shows that children on blockers experience a decline in bone density relative to the normal standard for their age group, and this decline was especially marked for girls. 

The conclusion of an analysis by Professor Carl Heneghan (2019) of all published studies of “gender affirming” hormone treatment was: “The current evidence base does not support informed decision making and safe practice in children.”

Despite a host of known and unknown risk factors — the unforeseen, exponential rise in referrals, especially of teenage girls, the change in presentation from childhood-onset to adolescent-onset gender dysphoria, with its associated co-morbidities, the emerging evidence that blockers may serve to create persistence, and recent evidence of irreversible harms to the developing brain — the GIDS trial has not been halted. 

In fact, quite the reverse: a trial with as yet no published result has been rolled out for all children and has come to be seen as the standard pathway for any child experiencing distress or confusion around their gender.

GIDS clinicians and senior members of staff have alerted journalists to their serious concerns, as documented in the Observer recently, and they deserve our serious attention. 

Any clinical treatment of children should be subject to the highest level of scrutiny and children experiencing gender dysphoria have a right to the same level of medical ethics and care as every other child.

Stephanie Davies-Arai is founder of the Transgender Trend website (


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