Troubling news for Fortnite-obsessives: The World Health Organization this week included "gaming disorder" as a new mental health condition in the 11th edition of its International Classification of Diseases. The WHO previously added the disorder in the draft for the ICD-11 earlier this year. Now it's official.

The revision comes at a time when public concern over technology abuse is high and rising. Spurred by the burgeoning digital wellness movement, Apple and Google both unveiled tools in recent weeks designed to help users monitor and manage the time they spend staring at screens, including parental controls that restrict the time kids spend playing games.

But while experts generally lauded Google and Apple's new tools as a step in the right direction, many of them have reservations about gaming disorder's inclusion in the ICD.

"I don't want there to be people classified with a mental disorder when they don't really have one," says University of Connecticut psychologist Nancy Petry, who in 2013 chaired the American Psychiatric Association subcommittee that considered adding "internet gaming disorder" to the latest edition of the Diagnostic and Statistical Manual of Mental Disorders. At the time, her group concluded there was too little evidence to list gaming addiction as a formal disorder, adding it instead to a section titled "Conditions for Further Study."

Today Petry, who is leading the first NIH-funded study on gaming addiction, believes the evidence is still insufficient. That puts mental health experts in something of a pickle. Truth be told, the most salient question isn't so much whether some people develop an unhealthy relationship with gaming. (Most experts agree that concerns over the allure of videogames are justified, that the subject deserves further study, and even that a small percentage of people may develop clinically problematic gaming habits.) It's whether the existing research is solid enough to warrant official classification from the WHO. Unlike the DSM, the ICD-11 has no provisional categories, no appendix in which to list potential disorders as requiring more research. It's all-or-nothing: A condition either goes in the ICD-11 or it doesn't. As such, critics argue, the burden of evidence for a disorder's inclusion, characterization, and treatment should be very high.

And at least right now, critics contend, that evidence doesn't exist for gaming disorders. Many existing studies on the subject are of surprisingly low quality. A large number of them are statistically underpowered, relying on small sample sizes, and do little do clarify whether videogames cause psychological problems or are merely associated with them.

"Some of these gaming habits are likely coping strategies to deal with other underlying psychological challenges," says Lennart Nacke, director of the Human-Computer Interaction Games Group at the University of Waterloo’s Games Institute.

These shortcomings are compounded by a lack of consistency across studies, not only in what they're measuring but how they measure it. "There’s well over 50 different self-report scales used to study gaming disorders," Petry says. In a very real sense, many gaming disorder researchers aren't even speaking the same language.

As a result, estimates of the extent of gaming disorders vary considerably. But studies that rely on the DSM's provisional criteria, which Petry helped develop, suggest that gaming disorder might affect between 0.3 and 1 percent of the population.

In absolute terms, that could translate to millions of people. (For reference: The National Institutes of Mental Health estimates the prevalence of schizophrenia and related psychiatric disorders to range between 0.25 and 0.64 percent in the US.) In other words: People with gaming disorders could very well constitute a clinically significant proportion of the population—a fact that only underscores the need for clear diagnostic criteria.