The Tavistock and Portman NHS Foundation Trust
A board report to the Gender Identity Development Service (GIDS) clinic in the UK obtained under the Freedom of Information Act reports results from suppressing puberty of 44 adolescents for one year. The full results were written up (and corrected) 5 years later in Carmichael et al (2021).
Biggs discovered that Costa et al. (2015) was part of a broader Early Intervention Study (EIS) on 50 adolescents given blockers between 2010 and 2014. Costa et al. report the study's nominally positive results but negative results from the study were not published. Additional outcomes for 44 of this cohort are available as an appendix in a 2015 GIDS board report and are excerpted below:
Results include a significant increase in self-harm (emphasis added):
Looking at two self-harm items measured by the [Youth Self Report], a significant increase was found in the first item “I deliberately try to hurt or kill self”. Adolescents had the option to score these items as: not true, sometimes true, often true. More adolescents tend to score this item in the “sometimes true - range” [after blockers] compared to [before blockers], especially natal girls.
Gender dysphoria did not improve:
No significant changes in gender dysphoria emerged...This suggests that the suppression of puberty does not impact positively on the experience of gender dysphoria.
Body image improved in boys and worsened in girls:
For body image however, significant differences were found looking at both sexes separately between T0 and T1...Natal boys were less dissatisfied with their primary sex characteristics after being on the blockers for 1 year...whereas natal girls appeared to be more dissatisfied with their secondary...and neutral sex characteristics.
A measure of physical well-being decreased:
Publication bias is when published results favour a specific narrative or direction. The discovery that negative results from the EIS were not published indicates research on puberty blockers has a publication bias.
Overall, no significant changes occurred in Health Related Quality of Life, except for one dimension completed by parents, which showed a significant decrease in Physical well-being of their child.
Blockers have no evidence of benefit and carry a risk of negative impacts across several dimensions.