If your teenage daughter suddenly declares herself transgender, should you assume she’s mature enough to make decisions that will permanently affect her health, fertility and future? Or could she be influenced by societal and peer pressure? Physician and researcher Lisa Littman doesn’t have the answer, but transgender ideologues are trying to silence her for even asking the question.

Dr. Littman’s study about transgender-identifying teens was published in the open-source, multidisciplinary scientific journal PLOS ONE last month. Her interest had been piqued in 2016, when she noticed an uptick in parental reports that teens had suddenly insisted their gender identity didn’t match their sex, although they’d shown none of the common prepubescent signs of the condition, known as gender dysphoria. She spoke to a clinician who’d observed the same trend. “When the characteristics of a population seeking care for a condition substantially changes, the responsible thing to do is to start asking questions about what might be contributing to these changes,” Dr. Littman says.

Since little is known about such “rapid-onset gender dysphoria,” the first step for researchers is to describe it and introduce topics for future inquiry. Dr. Littman surveyed 256 parents, whom she found online, collecting information about the teens’ mental health, friend-group dynamics and social-media use. Dr. Littman’s findings suggested these young people may have been driven in part by “social and peer contagion.”

Nearly 70% of the teenagers belonged to a peer group in which at least one friend had also come out as transgender. In some groups, the majority had done so. Nearly 65% of teens had spent an increased amount of time online and on social media, and parents reported that pro-transgender YouTube videos and blogs might have been influential.

Declaring oneself transgender carried social benefits, the parents reported. Among parents who knew their children’s social status, nearly 60% said the announcement brought a popularity boost. “Being trans is a gold star in the eyes of other teens,” one parent wrote.