Medical evidence underlying gender care for adolescents is “remarkably weak” and provides little clarity on long-term outcomes, according to an in-depth review of care commissioned by England’s state-funded National Health Service.

Gender care can include anything from counselling to medications related to gender issues, including drugs that can pause puberty.

The final report of the Cass Review, led by prominent pediatrician Dr. Hilary Cass and which includes research from independent academics at the University of York as well as input from families and clinicians was released on Wednesday.

The report concludes that young people with gender dysphoria — the distress of identifying as a gender different from the one assigned at birth — deserve better care but stresses that there is a lack of good evidence about how best to provide that.

The review was commissioned by the National Health Service in 2020, after the service — in line with other countries in Europe as well as the United States — saw increasing numbers of young people seeking gender care and differing opinions among experts about how best to help them.

The NHS has already announced that, in future, puberty-blocking drugs in England will only be available for young people experiencing gender distress in the context of a clinical trial. It acted after the Cass Review published interim recommendations in 2022. There is little detail yet on how this trial may work.

As part of plans to widen access to gender care and broaden the professionals involved, the NHS has also closed the previous provider of gender care for young people and replaced it with two new services in London and northwest England.

However, there is a huge backlog of cases after delays in getting services operational, and several thousand young people remain stuck in limbo on years-long waiting lists.

Prime Minister Rishi Sunak said he welcomed the “care and compassion” of the review.

“We simply do not know the long-term impacts of medical treatment or social transitioning… and we should therefore exercise extreme caution,” he said.

The Cass Review urges extreme caution around providing masculinizing or feminizing hormones before the age of 18.

But on social transition — changing names or pronouns — it concludes there is a lack of good evidence on the impact. It recommends professionals are consulted early on for pre-pubertal children, but for adolescents, “exploration is a normal process and rigid binary gender stereotypes can be unhelpful.”