A 2007 study supports earlier findings that bipolar disease is underrecognized, often improperly treated, and may be more accurately characterized as a spectrum disorder than a black-and-white disease. The study, published in the Archives of General Psychiatry, analyzed data from the National Comorbidity Survey Replication (NCS-R), a nationwide survey of mental disorders among 9,282 Americans ages 18 and older. The NCS-R was funded by the National Institutes of Health's National Institute of Mental Health (NIMH).

Spectrum subtypes

NIMH researcher Kathleen Merikangas, Ph.D., and her colleagues identified prevalence rates of three subtypes of bipolar spectrum disorder among adults. Bipolar I is considered the classic form of the illness, in which a person experiences recurrent episodes of mania and depression. People with bipolar II experience a milder form of mania called hypomania that alternates with depressive episodes.

People with bipolar disorder not otherwise specified (BD-NOS), sometimes called subthreshold bipolar disorder, have manic and depressive symptoms as well, but they do not meet strict criteria for any specific type of bipolar disorder noted in the Diagnostic and Statistical Manual for Mental Disorders (DSM-IV), the reference manual for psychiatric disorders. Nonetheless, BD-NOS still can significantly impair those who have it.

The results indicate that bipolar I and bipolar II each occur in about 1 percent of the population; BD-NOS occurs in about 2.4 percent of the population. The findings support international studies suggesting that, given its multidimensional nature, bipolar disorder may be better characterized as a spectrum disorder.

More targeted treatments

"Bipolar disorder can manifest itself in several different ways. But regardless of type, the illness takes a huge toll," said NIMH Director Thomas R. Insel, M.D. "The survey's findings reiterate the need for a more refined understanding of bipolar symptoms, so we can better target treatment.

Most respondents with bipolar disorder reported receiving treatment. Nearly everyone who had bipolar I or II (89 to 95 percent) received some type of treatment, while 69 percent of those with BD-NOS were getting treatment. Those with bipolar I or II were more commonly treated by psychiatric specialists, while those with BD-NOS were more commonly treated by general medical professionals.

However, not everyone received treatment considered optimal for bipolar disorder. Up to 97 percent of those who had some type of bipolar illness said they had coexisting psychiatric conditions, such as anxiety, depression, or substance abuse disorders, and many were in treatment for those conditions rather than bipolar disorder.

Along those lines, the researchers found that many were receiving medication treatment considered "inappropriate" for bipolar disorder (e.g., they were taking an antidepressant or other psychotropic medication in the absence of a mood-stabilizing medication such as lithium, valproate, or carbamazepine). Only about 40 percent were receiving appropriate medication, considered a mood stabilizer, anticonvulsant, or antipsychotic medication.

"Such a high rate of inappropriate medication use among people with bipolar spectrum disorder is a concern," said Dr. Merikangas. "It is potentially dangerous because use of an antidepressant without the benefit of a mood stabilizer may actually worsen the condition.

Better screening

Merikangas and colleagues speculate that as people seek treatment for anxiety, depression, or substance abuse disorders, their doctors, especially if they are not mental health specialists, may not be detecting an underlying bipolar condition in their patients.

"Because bipolar spectrum disorder commonly coexists with other illnesses, it is likely underrecognized, and therefore, undertreated. We need better screening tools and procedures for identifying bipolar spectrum disorder, and work with clinicians to help them better spot these bipolar symptoms," concluded Dr. Merikangas.

 


Sources:

National Institute of Mental Health (NIMH); National Institutes of Health (NIH).

Merikangas KR, et al. "Lifetime and 12-Month Prevalence of Bipolar Spectrum Disorder in the National Comorbidity Survey Replication." Archives of General Psychiatry. May 2007; 64.