Widening the definition of attention deficit hyperactivity disorder (ADHD) has led to an overdiagnosis of the condition, causing many people, especially children, to receive needless and potentially harmful medical treatment, according to a research analysis published online Wednesday in the journal BMJ (British Medical Journal).

The expansion of the definition of the disorder also threatens to create a skepticism about ADHD diagnoses that may harm people who have severe cases and “who unquestionably need sensitive, skilled specialist help and support,” warn the Australian and Dutch authors of the analysis.

ADHD is a disorder characterized by severe and frequent episodes of inattention hyperactivity or impulsivity. It’s most commonly diagnosed in early childhood, but can continue through adolescence and into adulthood.

Earlier this year, the Centers for Disease Control and Prevention reported that 6.4 million U.S. children between the ages of 4 and 17 — or about 11 percent of all school-aged children in the country  — had received a diagnosis of ADHD. Those statistics stunned many health professionals. The rate of ADHD had been previously estimated at 3 to 7 percent of all children.

Some of that rise may be due to clinicians becoming better at recognizing and diagnosing ADHD, acknowledge the authors of the BMJ paper. But research shows, they quickly add, that 86 percent of children diagnosed with ADHD in the United States have “mild” or “moderate” forms of the disorder. Less than 14 percent have severe ADHD.

“Severe cases of ADHD are obvious, but in mild and moderate cases — which constitute the bulk of all ADHD diagnoses — subjective opinions of clinicians differ,” the authors point out.

Evidence of this subjectivity — and how it can lead to overdiagnosis — can be seen in the unsettling finding that children whose birthdays fall in the latter part of the school year (who are, therefore, younger than many of their peers) are more likely to be diagnosed with ADHD than children born earlier in the year.

Unwanted side effects

In the United States, about 87 percent of children diagnosed with ADHD are prescribed a medication, mostly methylphenidates (such as Ritalin) and amphetamines (such as Adderall). Yet, as the authors of the BMJ paper point out, these drugs were developed for the treatment of severe, not mild or moderate, symptoms.

ADHD drugs are linked to serious side effects, including liver toxicity, weight loss, sleep problems, mood swings, and even thoughts of suicide. They can also interfere with growth.

In addition, children who are diagnosed with ADHD are at greater risk of being stigmatized and socially excluded. “Teacher and parent expectations of academic achievements are also low,” the authors of the BMJ paper note, “and these are associated with actual lower achievement scores.”

A loosening of diagnostic criteria

An important contributor to the expanding definition of ADHD — and the subsequent rise in the prevalence of the condition — has been the Diagnostic and Statistical Manual of Mental Disorders (DSM), sometimes referred to as the “bible” of psychiatry. With each new edition, the DSM has loosened its criteria for ADHD, leading to a subsequent jump in the number of children who receive a diagnosis.

The latest edition — DSM-5, which was released earlier this year — is no exception to this trend. It has widened the definition of ADHD in several ways, by including, for example, more behaviors that qualify as symptoms and by increasing the maximum age of the onset of symptoms from 7 to 12 years.

“These changes are a cause for concern because they increase the risk of confusing ADHD with normal development processes, such as pubertal restlessness and distractibility,” write the authors of the BMJ paper.

Other researchers have estimated that the prevalence of ADHD will rise more than 15 percent as a result of the diagnostic changes in the DSM-5.

Financial conflicts

Some 78 percent of the medical experts who participated in developing the DSM-5 guidelines for ADHD and other disruptive behavior disorders had financial conflicts of interest through ties to the pharmaceutical industry, report the authors of the BMJ paper.

“Whether this affected decisions regarding changes to ADHD criteria is unknown,” they add.

It’s been estimated that between $320 and $500 million is spent annually in the U.S. on medications for people inappropriately diagnosed with ADHD.

Answers remain elusive

“Despite extensive research into factors contributing to ADHD etiology, we are no closer to understanding the cause or causes of this disorder,” conclude the BMJ authors. “Social factors such as political environment, education funding, and disability services may contribute to seeking a diagnosis of ADHD and are under-researched.”

Until the causes of the disorder are more fully understood, the authors of the paper call for clinicians to use a six-step approach to diagnosing and treating the disease — an approach that refers children to a developmental pediatrician or psychiatrist for medications only after all other diagnostic possibilities and treatment options have been exhausted.

The paper can be downloaded and read at the BMJ website. Its authors are Rae Thomas, a senior research fellow at Bond University in Queensland, Australia;  Dr. Geoffrey Mitchell, a professor of general practice and palliative care at the University of Queensland; and Laura Batstra, a psychologist and researcher at the University of Groningen in the Netherlands.