It is easy to overlook the fact that over 90% of medical treatments are not backed by strong evidence. People can find it frustrating – even infuriating – when a review concludes that the evidence for a treatment is too weak to say whether it helps or harms.

This has been the case with the NHS England’s recent decision to restrict new prescriptions of cross-sex hormones for 16- and 17-year-olds.

The struggle to base clinical decisions on solid evidence is not new, nor is it unique to gender medicine. Archie Cochrane, a pioneering Scottish researcher, awarded obstetrics and gynaecology a wooden spoon in 1979 for the worst use of scientific evidence in clinical practice – a damning verdict that prompted the field to overhaul how it evaluated and applied research. It led to the first evidence-based textbook, a global movement and an online library.

Other medical fields have also struggled to meet this challenge, often through no fault of their own. Paediatrics, for example, faces a difficult balancing act when trying to produce clear, reliable studies.

To understand the complexities involved, look no further than your medicine cabinet. Paracetamol (acetaminophen) is considered the pain relief and antifever medicine of choice for infants and children. Weight-adjusted doses are scaled down safely from adult quantities, making it a versatile and trusted option across all age........

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