Sexual symptoms have long been known side effects of the popular Prozac class of antidepressants, but a growing body of research suggests that they are far more common than previously thought, perhaps affecting half or more of patients.

And a handful of recent medical and psychological journal articles document a small number of cases in which sexual problems remain even after a patient goes off the drugs.

“This is such an upsetting issue,” said Aline Zoldbrod, a Lexington psychologist and sex therapist. “There are people for whom SSRIs are really life-saving, I think, but the idea that someone would have to choose between getting out of the darkness of depression and having a good sex life is horrible.”