The Uk's NICE has conducted an evidence review of puberty blockers to assist the independent review lead by Dr Hilary Cass into gender identity services for children and young people. The evidence review was completed in October 2020 and published in March 2021.
The review team used a modified GRADE framework to assess the quality of the evidence for the following outcomes:
- gender dysphoria,
- mental health,
- body image, and
- psychosocial functioning.
The quality of evidence for all outcomes was rated as "very low". From the conclusion [emphasis added]:
"The results of the studies that reported impact on the critical outcomes of gender dysphoria and mental health (depression, anger and anxiety), and the important outcomes of body image and psychosocial impact (global and psychosocial functioning), in children and adolescents with gender dysphoria are of very low certainty using modified GRADE. They suggest little change with GnRH analogues from baseline to follow-up."
In the GRADE framework, treatments with "very low" evidence rating do not qualify for a guideline reccommendation. Its useful to contrast the NICE assessment with the Waikato Guidelines which state [emphasis added]:
"[t]here is good evidence that puberty blocking...significantly improves mental health and wellbeing outcomes"
The Waikato Guidelines cite Vries (2014) to support this statement, and go on to make a strong reccommendation to prescribe blockers.
The NICE review excluded Vries (2014) because the study population (and methodology) is the same as the original Vries (2011) study. The NICE team rate Vries (2011) as "very low certainity" across all outcomes.