In 2006, interest in attention deficit hyperactivity disorder (ADHD) reached new heights after a major study found that 4.4% of adults in America had the condition.
For decades, ADHD primarily had been a diagnosis in children, but the new study found it also affected as many as 10 million adults.
"It changed ADHD," said Peter Conrad, PhD, a professor of social sciences at Brandeis University who wrote The Medicalization of Society. "It became a lifespan disorder."
What happened next followed a familiar pattern: More research papers -- many of them based on research funded by drug companies -- were published.
The 2013 edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5), published by the American Psychiatric Association, relaxed the definition for adult ADHD.
The previous definition, in effect since 1994, said adults needed to have at least six of a possible nine symptoms from either of two categories. The symptoms include the inability to focus on tasks, fidgeting, and interrupting others. The new definition reduced it to five of the nine.
It also increased the age at which some of those symptoms first must have been present -- from before age 7 to before age 12.
Seventy-eight percent of those among the work group of experts who oversaw the changes had financial ties to the pharmaceutical industry, according to a 2012 analysis by the journal PLoS Medicine.
Psychiatrist Darrel Regier MD, MPH, a spokesman for the American Psychiatric Association, said financial conflicts were limited to $10,000 a year in income such as working as industry consultants, advisers, and speakers.
Regier, who served as vice chairman of the diagnostic manual's task force, defended the inclusion of adult ADHD in the document. He said that while it was once thought that children would age out of the disorder, for some, it remains in adulthood.
"Is it believable that this one mental disorder is one that kids would totally outgrow?" he said. "I think not."
Finally, the cumulative result of these factors was as expected: Prescriptions spiked.
And, since many of those drugs are amphetamines and stimulants that can lead to abuse, thousands more people began showing up in hospital emergency rooms.
At the same time, the growing focus on adult ADHD prompted questions from skeptics:
.How valid was the diagnosis?
.How many people are truly impaired?
.What role does promotion by drug-makers have in the rapidity of ADHD diagnoses?
.Has the spike in prescriptions for ADHD caused more harm than good?
"It is very easy to fake the symptoms of ADHD," said Daniel Carlat, MD, a psychiatrist at Tufts University School of Medicine and author of Unhinged: the Trouble with Psychiatry, a Doctor's Revelation about a Profession in Crisis.
A 2010 study found that 22% of adults tested for ADHD exaggerated their symptoms, exaggeration often made easier by the wide availability of online symptom check lists.
For years, the legitimacy of the adult ADHD was based on the belief that it was a condition that started in childhood and, for some, persisted into adulthood.
But last year that hypothesis was shaken by the publication of a provocative, long-term study that began in the early 1970s and followed more than 1,000 New Zealand children until age 38.
In that study Terrie Moffitt, PhD, a psychologist at Duke University, and her colleagues found that in childhood, 6% of those in the study had ADHD. At age 38, that number had dropped to 3%.
And the biggest surprise was the lack of evidence of significant overlap between the two groups.
Only 5% of those with ADHD in childhood still met the criteria at age 38. And only 10% of those who met the definition at age 38 were among those with the condition in childhood.
That, in turn, led the researchers to speculate that some of the adult patients were substance abusers who had attention problems stemming from drugs and alcohol, and that others may have had a personality disorder and were trying to game the system to obtain stimulants to abuse.
Moffitt noted that while childhood ADHD is considered a brain development condition, adult ADHD patients in her study scored normally on neuropsychological tests.
"It seems to be a different disorder," Moffitt said.
Adults with ADHD may have trouble completing tasks, prioritizing, and keeping appointments. Some research even shows a connection between the condition and higher rates of divorce, unemployment, and car accidents.
However, those only are associations, not proof that ADHD causes the problems or -- more importantly -- that ADHD drugs will prevent them.
In 2014, the pharmaceutical company Shire paid $56 million to settle a U.S. Department of Justice allegation that it illegally promoted Vyvanse and two other ADHD drugs, Adderall XR, and Daytrana.
Between 2007 and 2010, according to the Justice Department, company sales representatives claimed Vyvanse would prevent car accidents, divorce, arrests, and unemployment.