Bipolar disorder causes twice as much lost time on the job as does the far more prevalent depressive disorder, a study found.

Each U.S. worker with bipolar disorder averaged 65.5 lost workdays in a year, compared to 27.2 for major depression, the study by Harvard Medical School said.

The study, published in the current issue of the American Journal of Psychiatry, said that even though major depression is more than six times as prevalent, bipolar disorder costs the U.S. workplace nearly half as much -- an estimated $14.1 billion a year.

Researchers traced the higher economic cost mostly to bipolar disorder's more severe depressive episodes.

Copyright 2006 by United Press International