More than 4 percent of Americans have ever met diagnostic criteria for bipolar disorder, as compared with a worldwide average of about 2 percent, according to a study that conducted face-to-face interviews with 61,392 randomly selected people in 11 countries, published in the March Archives of General Psychiatry (Vol. 28, No. 3). Because the data were not based on medical-provider reports, the differences can’t be attributed to higher rates of assessment or diagnosis, the researchers note.

Lifetime prevalence rate