Drug industry is partly to blame for overdiagnosis of bipolar disorder, researchers claim

Marketing tactics by the drug industry are contributing to a huge overdiagnosis of bipolar disorder, researchers have said.

A team from Brown University in Rhode Island says it has evidence that fewer than half of patients who were given a diagnosis of the disorder actually had it (Journal of Clinical Psychiatry www.psychiatrist.com/abstracts/oap/ej07m03888.htm). Their finding contradicts previous claims that the illness was underdiagnosed.

Lead researcher Mark Zimmerman of Rhode Island Hospital and Brown University, said: “There might well be some cases where the condition goes undiagnosed.

“But the results from this study suggest that bipolar disorder is being overdiagnosed, and, given the serious side effects that the treatments can cause, we need to be aware of this.”

The study centred on psychiatric outpatients who received a diagnosis of bipolar disorder at Rhode Island Hospital between May 2001 and March 2005. The researchers discovered that in fewer than half of the 145 patients (43%) the diagnosis was made according to the relevant gold standard, the structured clinical interview for DSM-IV (SCID).

Subsequent investigations found that patients whose illness had not been diagnosed according to SCID almost certainly did not have bipolar disorder.

“The marketing tactics of drug companies are absolutely a contributing factor,” Dr Zimmerman told the BMJ.

“You cannot go to a meeting on bipolar disorder that doesn’t have a big discussion right at the start about how underdiagnosed this illness is and how doctors need to ensure that patients are treated.

“These meetings are usually sponsored by drug companies, and I think they must be having an effect on doctors.”

He added: “I think it’s reasonable to assume this is happening elsewhere. I’ve have spoken to several other doctors who also think it’s happening where they are.”

His paper also says that advertising directly to the consumer in the United States has meant that patients are prompting their doctors to consider a diagnosis of bipolar disorder that may be inappropriate.

As a result of “the campaign against under-recognition,” some anxious, agitated, or irritable and depressed patients with insomnia and racing thoughts are being given a misdiagnosis of bipolar disorder, the study claims.

Last September the BMJ reported that the number of people in the US aged under 20 who had received a diagnosis of bipolar disorder had grown 40-fold between 1994 and 2003 (BMJ 2007;335:535 doi: 10.1136/bmj.39335.363137.DB). The researchers, from Columbia University, said at the time that it wasn’t clear whether previous underdiagnosis or current overdiagnosis was to blame for the surge in the number of cases.

Marjorie Wallace, chief executive of the UK mental health charity Sane, said, “There are some concerns that we are overdiagnosing and over-medicalising depression, including bipolar illness.

“But we also shouldn’t forget that failing to identify the condition can have extremely damaging consequences.”

Ken Johnson, of the trade organisation Pharmaceutical Research and Manufacturers of America, said, “Where we don’t see eye to eye is the researchers’ assertion that overdiagnosis of this disorder is a greater problem, particularly when the National Institute of Mental Health last year suggested that bipolar disorders are often under-recognised.”