The U.K. National Health Service received an independent review on gender-related medical treatment for young adults and minors that was submitted on Wednesday. It found “poor-quality” studies and “very little evidence” on the long-term effects of medicalized transition.

Hilary Cass wrote in her introduction that “this is an area with remarkably weak evidence.” People on both sides of the argument exaggerate or misrepresent the results of studies to support their position. The reality is we don’t have good evidence about the long-term effects of interventions for managing gender-related distress.

NHS England commissioned an Independent Review of Gender Identity Services for Children and Young People by 2020. In the report, a “young adult”, is a person between 18 and 30 years old.

The report is sometimes referred to as the “Cass Report,” or “Cass Review,” and indicates that the number children and young persons presenting themselves at the NHS Gender Identity Service has increased since 2009. It also shows an “exponential increase” in 2014.

The number of adolescent girls referred to GIDS increased from 15 to 1071 from 2009 to 2016. And the number female children referred increased from 2 to 138. The number of adolescent boys rose from 24 up to 426 and the number male children increased from 10 to 131. Before 2009, GIDS treated fewer than fifty children a year and performed fewer medical procedures.

The report states that “a common explanation given is that there is greater acceptance” for the increase in presentations. The report states that “while it is true that trans identities are more accepted, especially among younger generations, this may explain some of the rise in numbers. However, the exponential growth in referrals in a relatively short timeframe of five years is much faster than what would be expected of normal acceptance for a minority group.”

The report recommends children and adolescents referred to NHS services for gender-related issues receive a “holistic evaluation” which includes screening for “neurodevelopmental disorders, including autism spectrum disorders, and a psychological assessment.”

The report says that “the focus on using puberty blocks for managing gender-related stress has overshadowed other evidence-based treatment options which may be more effective.” The interim report released in February 2020 did not include any guidance on hormone treatment “due gaps in the evidence-base.”

According to the Cass Report, the available evidence does NOT suggest that hormone therapy reduces the risk of suicide.

NHS practitioners can currently provide masculinizing or feminine hormones to 16-year-olds and older. The report recommends that “an extremely careful clinical approach” and “a strong clinical justification” be used when administering masculinizing or feminine hormones to anyone under 18 years old.

The report notes that the number of people who are treated with hormones and then de-transition is likely to increase, but the exact percentage remains unknown due to the lack of studies on long-term effects.

The report suggests a “tiered” approach to intervention that “addresses the urgent risk,” relieves mental-health concerns so that young people can “make complex choices,” and develops an action plan which may include “any combination of physical, social and psychological interventions.”

The report states that “the current evidence base indicates that children who exhibit gender incongruence as a child are most likely going to stop before puberty. However, for a few of them the incongruence may persist.” Parents and families require support and guidance on how to best support their children, in a non-judgmental and balanced way.

The Cass Report drew on systematic reviews, NHS data, meetings, focus groups and other resources.

The report states that “although some people think the clinical approach is based on social justice, the NHS operates in a way that is evidence-based.”