Is bipolar disorder overdiagnosed among patients with substance abuse?

A new study found a 57% false positive rate:

The study was performed at a residential treatment facility for patients with known substance abuse or dependence. All consecutive patients who presented to the psychiatrist affiliated with the facility with a request for ongoing psychiatric care for a previous diagnosis of BD were asked to participate. To qualify for the study, patients had to have either a history of treatment for BD by a psychiatrist or be in current treatment for BD as an outpatient. In other words, all subjects had to have been diagnosed or treated for bipolar illness by a psychiatrist.

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All potential subjects participated. A total of 21 patients were interviewed....Only 9 of the 21 (42.9%) participants met DSM-IV criteria for BD.