Until just a few years ago, gender dysphoria - severe discomfort in one's biological sex - was vanishingly rare. It was typically found in less than .01 percent of the population, emerged in early childhood, and afflicted males almost exclusively. But today whole groups of female friends in colleges and schools across the world are coming out as 'transgender'. These are girls who had never experienced any discomfort in their biological sex until they heard a coming-out story from a speaker at a school assembly or discovered the internet community of trans 'influencers'.

Unsuspecting parents now find their daughters in thrall to YouTube stars and 'gender-affirming' educators and therapists, who push life-changing interventions on young girls - including medically unnecessary double mastectomies, and hormone treatments that can cause permanent infertility. Abigail Shrier, a writer for the Wall Street Journal, has talked to the girls, their agonised parents, and the therapists and doctors who enable gender transitions, as well as to 'detransitioners' - young women who bitterly regret what they have done to themselves.

Coming out as transgender immediately boosts these girls' social status, Shrier finds, but once they take the first steps of transition, it is not easy to walk back.