Many Depressed Patients Have Bipolar Disorder

October 18, 2004

Oct. 18, 2004 (Montreal) — Many depressed patients who fail to respond to repeated treatment with antidepressants may actually have bipolar disorder, according to new research. These patients are better treated with mood stabilizing drugs, possibly in combination with atypical neuroleptics.

Clinicians who treat patients with depression are all too familiar with those who do not seem to respond to antidepressants or who respond for a while and then relapse. According to Verinder Sharma, MB, FRCP(C), many of these patients probably have bipolar disorder. Dr. Sharma is a psychiatrist at the Mood Disorders Program of St. Joseph's Health Care and a professor of psychiatry at the University of Western Ontario in London, Ontario, Canada. He presented his research into misdiagnosed bipolar disorder here at the 54th annual meeting of the Canadian Psychiatric Association.

Depressed patients with bipolar features are both less likely to respond to antidepressants and more likely to have tolerability problems with these drugs, possibly because they elicit hypomanic symptoms such as agitation and sleep disturbance, said Dr. Sharma. What is less known is whether these bipolar features are subtle enough for clinicians to miss them if they are not careful.

"There are a lot of diagnoses for which we really have to do better screening," Dr. Sharma told Medscape. "What is happening is sometimes people overemphasize the issue of cross-sectional symptoms, whereas with mood disorders, we really have to look at people over a period of time in order to know what we're dealing [with]. So, [for] some of these people, it's possible that at some point they were clearly unipolar, but when we observe them over a period of time, it's more clear [that they have bipolar features]."

In addition to poor response to antidepressants, signs that seemingly depressed patients may have bipolar disorder include an early age of onset, the presence of multiple episodes over a long period of time, a family history of bipolar disorder, a history of postpartum depression, a history of psychotic symptoms, and a hyperthymic personality when not depressed.

One challenge is the changing definition of bipolarity. "What we have seen over the past few years is the expansion of the bipolar spectrum," said Dr. Sharma. It may be helpful to look at unipolar depression and bipolar disorder as opposite ends of a continuum, rather than distinct diseases, he added.

Dr. Sharma and colleagues used the Structured Clinical Interview for the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) to reinterview 61 patients diagnosed with unipolar depression who had failed to respond to at least two adequate courses of antidepressants. By examining their symptoms over time as well as their family history, the researchers discovered that 35% of these patients had a form of bipolar disorder. Even more remarkably, after following them for a year, fully 80% of patients were deemed to have bipolar disorder.

"In a large number of these patients, we were able to stop antidepressants and to treat them with mood stabilizers, usually in combination with neuroleptics," said Dr. Sharma during his presentation. Specifically, 93% of patients were taking antidepressants at intake compared with 34% after one year of follow-up. The other 66% were taking mood stabilizers, often combined with atypical neuroleptics. Many of those who remained on antidepressant therapy had been switched to monoamine oxidase inhibitors.

"We urge caution about the use of antidepressants in patients who have a history of loss of response because, in these patients, some of them developed treatment-refractory symptoms because of the overuse or misuse of antidepressants," Dr. Sharma said during his presentation.

"There may be a subgroup of people in whom we may be contributing to treatment refractoriness by giving them antidepressants," Dr. Sharma told Medscape. "In these people, you really have to be using mood stabilizers."

CPA 54th Annual Meeting: Paper PS7E. Presented Oct. 16, 2004.

Reviewed by Gary D. Vogin, MD

Alison Palkhivala is a freelance writer for Medscape.

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