(NewsNation) — For adults, getting an accurate diagnosis of attention deficit hyperactivity disorder (ADHD) can be a frustrating ordeal due to a lack of clear clinical guidelines in the U.S.

ADHD is one of the most common psychiatric disorders among adults, yet many health care providers have uneven training on how to evaluate it properly. The latest edition of the American Psychiatric Association’s diagnostic manual provides some criteria, but experts say it is incomplete, The New York Times reported.

The diagnostic manual, the D.S.M., requires significant ADHD symptoms, like inattention and impulsivity, to be present in at least two settings before age 12. However, some adults don’t recall childhood symptoms or had milder cases.

The D.S.M. also doesn’t formally include emotional dysregulation and executive function deficits that adults with ADHD commonly experience, like mood issues and problems with planning and organization.

Dr. David W. Goodman, an assistant professor of psychiatry and behavioral sciences at the Johns Hopkins University School of Medicine, is working on the first U.S. clinical guidelines for diagnosing and treating adult ADHD to create a more uniform process, according to the NYTimes.

The guidelines, expected for public comment later this year, aim to provide clarity amid new research, per the NYTimes.

Proper adult diagnosis typically requires interviews, developmental history, symptom questionnaires and discussing symptoms with the patient’s family. Several factors like digital technology use and coexisting conditions can complicate evaluations.

Without clear rules, some well-intentioned providers are “making it up as they go along,” Goodman said, leaving some adults undiagnosed and others potentially misdiagnosed and improperly medicated.