Vries et al, 2014

Young Adult Psychological Outcome After Puberty Suppression and Gender Reassignment


The researchers report psychological outcomes from ~40 adolescents (15 male and 25 female) from an original cohort of 111 through treatment with psychological support, puberty blockers, cross-sex hormones, and surgery at a Dutch clinic. The cohort is the same as the one reported in Vries et al., 2011.

The researchers measure various psychological outcomes at three stages: the introduction of puberty blockers, the introduction of cross-sex hormones, and one year after surgery.


Biased Study Design

Of the original 111 given puberty blockers, 70 went on to take cross-sex hormones between 2003 and 2009 Vries et al., 2011. It is not clear what happened to the 41 who did not, who seem to have either withdrawn or went on to take cross-sex hormones at a later date.

The researchers excluded 15 of the remaining 70 for various reasons:

  • Six were not yet one year after surgery or did not choose to have surgery.
  • Two refused to participate.
  • Two did not return questionnaires.
  • Three were ineligible for surgery (e.g. morbid obesity).
  • One died from postsurgical necrotising fasciitis.

This left 55 participants in the study at the initial period. Aside from the lack of control and confounding with psychological support, the exclusions give the results a high degree of bias (Chew et al., 2018). The 41 may have delayed or withdrawn from the study due to poor outcomes. For the six who missed the cutoff for completed surgery, regret and poor psychological outcomes may have contributed to the decision not to pursue surgery. Similarly, subjects who refused or did not return questionnaires may have done so because they also had poor outcomes. Conditions that made participants ineligible for surgery, such as obesity, are also known to be comorbid with poor psychological functioning.

The study does not report outcomes for all 55 particpants because the authors did not gather all outcome measurs for all participants at all three stages. This left between 32 and 45 participants reporting outcomes depending on the specific measure.

The study excluded the subjects most likely to have had poor psychological outcomes and then measured outcomes in the remaining group. The fact that one young person died as a result of sex characteristics surgery does not enhance the case for medical interventions.

Mixed Results

Psychological outcomes were neutral to negative during pubertal suppression.

Gender dysphoria and body image difficulties persisted during pubertal suppression, and female adolescents had greater body dissatisfaction. Statistically significant improvements in body image perception and gender dysphoria occurred one year after surgery.

Quoting the relevant sections on pubertal suppression:

[Gender dysphoria] and body image difficulties persisted through puberty suppression.

Transmen reported more dissatisfaction with secondary and neutral sex characteristics [after pubertal supression]… — p. 699

For further analysis of the results of the study see Biggs, 2020.

Comparison with The New Zealand Guidelines

Compare the above to statements in the New Zealand Guidelines where they reference Vries et al. (2014) (emphasis added):

There is good evidence that puberty blocking and gender affirming care for trans young people significantly improves mental health and wellbeing outcomes. [Vries et al., 2014]

— p. 17

Puberty blockers halt the continuing development of secondary sexual characteristics, such as breast growth or voice deepening, and relieve distress associated with these bodily changes for trans young people. [Vries et al., 2014]

— p. 29

These claims are false and fail on several counts:

First, on what set of standards are the guideline authors basing their claim of “good evidence”? Evidence-Based Medicine (EBM) requires rigorous assessment of multiple studies before claims of “good” or “high quality” evidence can be made. For example, PHARMAC rejects any studies that are not well-conducted meta-analyses, systemic reviews, or high quality randomised controlled trials. Chew et al. (2018) rate the same study with a high risk of bias i two domains.

Second, the first statement (p. 17) elides the distinct potential outcomes attributed to pubertal suppression or surgery specifically.

Third, the NZ Guidelines attribute improvements to puberty suppression. However, without a control we cannot know if the changes were due to the treatment, the concurrent psychosocial support, or maturation as the participants aged.

Fourth, the second statement claims that blockers “relieve distress” These claims are not made by the referenced study, which reports negative results in the case of females.


A lack of control, the confounding effects of psychological support, and biased study design limit the study’s conclusions. Puberty blockers may have worsened body image perceptions in female participants.

The authors of the NZ Guidelines make false statements about the evidence for puberty blockers. Medical professionals cannot rely on the NZ Guidelines for unbiased research summary when gaining informed consent from parents.