A push by some mental-health researchers to define a new attention disorder has others concerned about overdiagnosis.

More than six million children in the U.S. have been diagnosed with attention deficit hyperactivity disorder (ADHD), and that number has been increasing steadily in recent years. Now, some mental health researchers are pushing for acceptance of a second attention disorder, raising concerns about overdiagnosis and overtreatment of these types of conditions.

Known as sluggish cognitive tempo (SCT), this newly proposed disorder is characterized by a specific set of physical and mental symptoms, including drowsiness, daydreaming, lethargy, mental confusion, and slowed thinking or behavior. Some researchers estimate that SCT affects 5.1 percent of U.S. adults, and, according to a recent article in The New York Times, some two million children.

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In spite of the controversy that acceptance of sluggish cognitive tempo is creating, the symptoms of the disorder have been recognized since the 1980s as a subtype of ADHD.

“SCT refers to a cluster of symptoms thought to be either a subset of ADHD or perhaps a ‘new’ disorder and has been receiving increasing attention by researchers. However, it is not even mentioned in the DSM-5,” says Dr. Robert Myers, an associate clinical professor of psychiatry and human behavior at the University of California, Irvine School of Medicine and creator of the Total Focus program. DSM-5 is the latest version of the Diagnostic and Statistical Manual of Mental Disorders, the American Psychiatric Association’s official guide for diagnosing mental disorders.

As any parent whose child daydreams often during class, doesn’t turn in work, or skips questions on exams can tell you, the symptoms proposed for SCT are real. The cause of the debate in the research arena is whether this collection of symptoms is different enough from ADHD to become a distinct disorder.

“Research findings vary as to whether SCT is a distinct disorder, a subset of ADHD, or a condition that may be comorbid [that may coexist] with ADHD,” says Myers.

This distinction is more than just one of labeling. How these symptoms are grouped will affect not only how people are diagnosed, but also how they are treated—and how pharmaceutical companies will market their new and existing drugs.

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Many children diagnosed with ADHD are not hyperactive, but are instead inattentive.

Recent research, including most of the papers published in the January 2014 issue of the Journal of Abnormal Child Psychology, argue that it is not useful to classify children with symptoms such as daydreaming and lethargy as having inattentive ADHD.

“Evidence to date, including the many findings in this special issue, is nearing a critical mass that likely supports the conclusion that SCT is a distinct disorder of attention from ADHD,” writes Russell Barkley, a longtime ADHD researcher and a psychologist at the Medical University of South Carolina, “yet one that may overlap with it in about half of all cases.”

In spite of the overlap between what is being defined as SCT and inattentive ADHD, many researchers are convinced that they are distinct. In studies of both children and adults, sorting people by the symptoms of SCT produces a more homogenous group, rather than the mishmash that occurs when the ADHD criteria are used.

So even though some people could be classified with both disorders, proponents of the new classification say that SCT has several distinct features from the noninattentive types of ADHD, including differences in which parts of the brain are affected.

“Data with respect to overlapping symptoms suggested that ADHD was associated with more severe and pervasive executive functioning deficits,” says Dr. Lee Ann Grisolano, a pediatric neuropsychologist, “while SCT played a more debilitating role in community and leisure arenas.”

“The research being conducted to better understand distinctions between SCT and ADHD is extremely important for purposes of predicting impairment in daily functioning, whether in school or in adult workplaces,” says Grisolano.

In addition to a more-accurate diagnosis, better medications would be needed to treat symptoms specific to SCT.

“It has been difficult to find effective medications for children with ADHD-Inattentive subtype,” says Grisolano. “Time and more research will tell what medications may or may not be best to treat SCT.”

The eventual acceptance of SCT will depend on whether it’s included in the next version of the Diagnostic and Statistical Manual of Mental Disorders. Given that DSM-5 was more than a decade in the making, it will be a long while before the final answer is in. This will give researchers more time to define the symptoms of SCT and ensure that it is truly distinct from ADHD.

Even though the fate of SCT is far from resolved, researchers recently helped pharmaceutical company Eli Lilly test its ADHD drug Strattera to see if it could improve the symptoms of this breakaway disorder. The results were published last year in the Journal of Child and Adolescent Psychopharmacology.

The fact that drug companies are already funding studies of their current drugs to treat a new, yet-to-be-recognized disorder has some people worried that acceptance of SCT will provide yet another reason for children to be diagnosed for behaviors like daydreaming, which could simply be a part of normal childhood life.

“As a clinical child and adolescent psychologist, my concern is that we continue to look for labels to put kids in boxes,” says Myers, “when what we should be doing is look at the child as an individual and identifying the specific psychological functions in that child that are causing problems with learning, emotions, or behavior and address those through targeted therapy and, when necessary, medication.”

It is also difficult to know exactly how many children would be diagnosed with SCT, especially given that the number of children currently diagnosed with ADHD is more than twice the estimates outlined in the DSM-5.

“It is possible that some children once diagnosed with ADHD-inattentive subtype would come to ‘lose’ that diagnosis and instead be diagnosed with SCT,” says Grisolano. “However, in my view, it is the understanding of the symptoms that lead to effective interventions, rather than the nomenclature chosen to describe the symptoms, that should be the primary focus.”

According to The New York Times, though, in addition to two million children moving from a diagnosis of ADHD to one of SCT, another one million who don’t fit ADHD’s criteria now could also be included.

“Medication is the most expedient method for treating ADHD and can be very effective,” says Myers. But “there is a growing consensus that it is overused and that psychological interventions and appropriate accommodations at school should be tried more often.”