Abraham Lincoln is etched in the nation's memory as a calm and reflective man. But only a few years before Lincoln became president of the United States, he was quite different in temperament and known for fits of intense anger. According to research published in the Summer 2001 issue of Perspectives in Biology and Medicine, pills Lincoln took for depression were likely to blame.

"We wondered how a man could be described as having the patience of a saint in his fifties when only a few years earlier he was subject to outbursts of rage and bizarre behavior," Norbert Hirschhorn, lead author of the study, says. His team suspected that blue massa common 19th-century antidepressantmight have exposed Lincoln to mood-altering doses of the heavy metal mercury.

To find out just how poisonous blue mass actually was, the scientists produced a sample of the medication, following a 19th-century recipe. In addition to mercury, the ingredients called for liquorice root, rose water, honey, sugar and dead rose petals. The scientists mixed the contents using an old-fashioned mortar and pestle and rolled the pills to size. Physicians normally recommended that patients take two or three pills a day.

Hirschhorn and colleagues discovered that two pills would have released into the stomach an amount of mercury vapor 40 times higher than what the U.S. National Institute of Occupational Health now considers safe. Two pills would have delivered an additional 750 micrograms of solid mercury; the Environmental Protection Agency considers 21 micrograms to be the maximum safe daily dose.

"Mercury poisoning certainly could explain Lincoln's known neurological symptoms: insomnia, tremor and the rage attacks," co-author Robert Feldman of Boston University says. And according to Feldman, the behavioral effects of mercury poisoning could have been reversible, which would explain why Lincoln calmed down after he stopped using the medication in 1861. "The wartime Lincoln is remembered for his self-control in the face of provocation, his composure in the face of adversity," Hirschhorn says. "If Lincoln hadn't recognized that the little blue pill he took made him 'cross' and stopped the medication, his steady hand at the helm through the Civil War might have been considerably less steady."