Over a third of children placed on puberty blockers by Britain’s controversial Tavistock child gender clinic suffered mental health problems after taking the hormone-altering drugs, according to fresh analysis.

A new look at a 2011 study conducted by the University College London Hospitals (UCLH) and the Tavistock Centre’s Gender Identity Development Service — the UK’s only child gender transition clinic that is set to be shut down over safeguarding failures — has found that the mental health of 34 per cent of children placed on puberty-blocking drugs “reliably deteriorated”, while 37 per cent saw no difference, and 29 per cent “reliably improved” following the administering of the drugs.

The new findings fly in the face of the 2011 analysis of 44 children aged between 12 and 15 years old which claimed that there had been “no changes in psychological function” after the youngsters were put on puberty blockers. While the original analysis was based on averages of groups based on questionnaires provided to the children and their parents, the new findings were based on individual results, The Telegraph reported.

Professor of psychology and sociology in the School of Health and Social Care at the University of Essex, Susan McPherson and retired social scientist David Freedman — who led the new inquiry — said that their methodology provides a “greater indication as to variation across participants”

“This complementary analytic approach allows us to look at how a treatment is performing in terms of the percentage of patients improving, deteriorating and showing clinically significant change,” the researchers said.

“It is possible, using this approach, to look at patterns, such as who is benefitting and who is not,” they continued. “We recommend that these approaches be incorporated into new GD [gender dysphoria] services being established in the UK as well as new research studies being designed.”

Last year, the National Health Service (NHS) ordered that the Tavistock Centre and its controversial Gender Identity Development Service (GIDS) be shut down by this year after an interim independent review from Dr Hillary Cass found that the treatments offered were “not a safe or viable long-term option” for children. However, the closure of the GIDS has been delayed until March of next year.

The gender clinic has faced criticism from whistleblowers, including from the former governor of the Tavistock and Portman NHS Foundation Trust, Dr David Bell, who revealed last year that clinicians would make determinations on whether to put children on hormone-altering drugs under dubious pretences, such as if young girls failed to show interest in “pink ribbons and dollies“.

The full report from Dr Hillary Cass’ team said that it will be taking into account the latest findings in its final report, which is expected to be published by the end of the year. The interim report has already resulted in significant changes to the treatment of allegedly transgender children, including the NHS prohibiting children from being placed on puberty blockers except under special circumstances, such as clinical trials.

Responding to the new findings, a spokesman from Tavistock and Portman NHS Foundation Trust said: “We are grateful to all of the clinicians and academics who have contributed to this study over the years, and we welcome new peer-reviewed analyses of the evidence around how to support these young people.

“The analysis plan for the original study was independently produced by experts in medical statistics, and the underlying data was published so that other researchers might conduct further analyses.”