I have a rare and painful genetic respiratory disorder called primary ciliary dyskinesia. I was 23 when doctors diagnosed my condition, but I had been sick my whole life . Again and again, I was told that I was suffering from nothing more than stress — that it was all in my head.

This is a common experience for young women. We have long known that women with some conditions are more likely than men to be under-treated for pain, and that doctors are more likely to dismiss reports of illness as psychosomatic when they come from women. Now, a recent study from Yale researchers shows how early this gender bias starts. The study found that when adult participants were asked to rate the perceived pain of a child receiving a finger prick to draw blood, they attributed more pain to the child they thought was a boy than they did to the child they thought was a girl.

The study’s authors associate these findings with “explicit gender stereotypes” that characterize men as more stoic about their pain and women as more emotional — and therefore, less credible.

An estimated 20 to 35 percent of adolescents experience chronic pain. According to a 2017 study, doctors are significantly more likely to dismiss the pain symptoms of young female patients than those of male ones. This can cause lasting damage to the relationships between doctors and their patients.