About 4 percent of people in the United States experience bipolar disorder at some point in their lives, according to the National Institute of Mental Health. And an estimated 2.8 percent of adults have been diagnosed with the disorder in the past year.

But in recent years, some researchers have called some of those diagnoses into question, while others have maintained that the number of people with bipolar disorder, which causes severe swings in energy levels and mood, is actually greater.

review of research published in February 2016 in TheCanadian Journal of Psychiatryconducted by Mark Zimmerman, MD, a professor of psychiatry and human behavior at Brown University in Providence, Rhode Island, looked at the overdiagnosis and underdiagnosis of bipolar disorder.

Dr. Zimmerman, who directs the Rhode Island Methods to Improve Diagnostic Assessment and Services Project (the MIDAS project), examined more than 20 years of results and data from MIDAS and determined that bipolar disorder is often overdiagnosed, and that more complete and accurate diagnostic evaluations could reduce the number mis- and overdiagnoses, as well as improve the detection of conditions related to bipolar disorder.

His review looked at results from one of his earlier studies, published in 2008 in the Journal of Clinical Psychiatry, which suggested that bipolar disorder is often diagnosed in people who don’t actually have the condition. In that large study, his research team determined that fewer than half the people in the study who said they had been diagnosed with bipolar disorder met the clinical criteria for the illness.

According to Zimmerman, the earlier study also revealed that some people who met the criteria for bipolar disorder had never been diagnosed with it. But far more people had been given the bipolar label by mistake, he says. Zimmerman believes part of the reason for this overdiagnosis trend is aggressive marketing to doctors by companies that produce the drugs used to treat bipolar disorder.

“When a pharmaceutical company repeatedly says, ‘Don’t miss bipolar disorder, don’t miss bipolar disorder, and when you diagnose it, here are some medications you can use to treat it,’ there’s a tendency to expand the concept,” Zimmerman says. According to the 2016 research review, the limited amount of time that some clinicians spend with patients could also be a factor in diagnoses that aren’t correct.

In addition, Zimmerman says, bipolar disorder shares some symptoms with borderline personality disorder, a condition marked by impulsive behavior and problems relating to other people — and because of this, people who have borderline personality disorder are often misdiagnosed as bipolar. Indeed, a review published in 2013 in The Scientific World Journal pointed to borderline personality disorder as a factor in the overdiagnosis of bipolar disorder.

The Potential Dangers in Being Misdiagnosed

People misdiagnosed with bipolar disorder may experience health setbacks as a result of the drugs used to treat it. Medication, including atypical antipsychotics, can increase the risk for high cholesterol and diabetes, Zimmerman says. Some medication has also been linked to thyroid and kidney problems, he adds.

Up to 20 percent of people with bipolar disorder may be mistakenly diagnosed with depression by their primary care doctors, according to a study published in July 2011 in the British Journal of Psychiatry. And a study published in February 2013 in the journal Acta Psychiatrica Scandinavica found a gap of almost 10 years, on average, between the participants’ first onset of bipolar symptoms and their first treatment with a mood-stabilizing medication.

These findings aren’t surprising, says Jeremy Schwartz, a psychotherapist in Brooklyn, New York. Bipolar disorder can be hard to diagnose, he says, because people often seek professional help only during their down periods and neglect to mention their up, or manic, periods.

“The manic side of bipolar disorder isn’t always bothersome to people,” Schwartz says. “They have more energy, and more motivation to do things. So the mental health professional doesn’t always hear about it.”

In addition, some younger people with bipolar disorder may have experienced depression but not yet had a manic episode. So a misdiagnosis of depression is sometimes given simply because a person has not yet experienced mania.

As a consequence, Schwartz says, those with bipolar disorder are often misdiagnosed with depression and may be given inappropriate treatment.

“When bipolar disorder is missed, people can be put on medication that actually worsens the manic symptoms,” Schwartz says. “So people end up waiting much longer to get the stability in their life that they’re looking for.”