A recent study funded by the National Institutes of Health’s (NIH) National Institute of Mental Health (NIMH) has found that bipolar disorder costs twice as much in lost productivity as major depressive disorder (MDD).

Each US worker with bipolar disorder averaged 65.5 lost workdays per year, compared to 27.2 for those with MDD. Even though major depression is six times more prevalent, bipolar disorder costs the American workplace nearly half as much – a disproportionately high $14.1 billion per year. Researchers discovered the higher toll is mostly attributed to bipolar disorder’s more severe depressive episodes rather than its agitated manic periods.

The new study, conducted by Dr. Philip Wang and Dr. Ronald Kessler of Harvard University, and colleagues, is the first to distinguish the impact of depressive episodes due to bipolar disorder from those due to MDD on the workplace. It is based on one-year data from 3378 employed respondents to the National Comorbidity Survey Replication (NCS-R), a nationwide household survey of 9,282 adults conducted from 2001-2003.

The investigators measured the persistence of the disorders by asking respondents how many days during the past year they experienced an episode of mood disorder. They judged the severity based on symptoms during a worst month. Lost work days due to absence or poor job performance, combined with salary data, yielded an estimate of lost productivity due to the disorders.

Poor functioning while at work accounted for more lost days than absenteeism. Although only about 1% of workers have bipolar disorder in a year, compared to 6.4% with MDD, the researchers projected that bipolar disorder accounts for 96.2 million lost workdays and $14.1 billion in lost wage-equivalent productivity, compared to 225 million workdays and $36.6 billion for major depression annually in America.

Around three-quarters of bipolar subjects had experienced depressive episodes over the past year, with about 63% also having agitated manic or hypomanic episodes. The bipolar-associated depressive episodes were much more persistent – affecting 134-164 days – compared to only 98 days for major depression. The bipolar-associated depressive episodes were much more severe as well, with measures of lost work performance consistently higher among workers with bipolar disorder who had major depressive disorder.

Dr. Wang said, “Major depressive episodes due to bipolar disorder are sometimes incorrectly treated as major depressive disorder. Since antidepressants can trigger the onset of mania, workplace programs should first rule out the possibility that a depressive episode may be due to bipolar disorder.”

He went on to say that future efficacy trials may be able to gauge the return on investment for employers offering coordinated evaluations and treatment for both mood disorders.

The study is published in the September 2006 issue of the American Journal of Psychiatry.

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