Understanding Bipolar Disorder and who is affected by bipolar disorder. Bipolar Disorder is affecting over 2 million American adults. This averages out to be about one percent of the population over the age of 18. Normally this disorder develops in late adolescence or early adulthood, but many people have their first symptoms during childhood and others may develop this condition later in life. About-bipolar-disorder.com~Site InfoWhoisTrace RouteRBL Check