Yet embracing I.G.D., as it’s known, as a new mental health disorder has its own perils. Many psychologists are skeptical that it exists at all as a stand-alone problem. The diagnostic criteria are still fuzzy, and the potential for overdiagnosis is enormous.

I.G.D. is a case study in what happens when researchers become convinced that a bad habit has become something different: a disorder. The studies pile up and the notion takes on a life of its own — one that may or may not be persuasive to putative “patients.”

“The question is, what’s the difference between a bad habit and a disorder, and where do you draw that line,” said Scott Lilienfeld, a professor of psychology at Emory University.