Neuroscience for Kids - Lincoln, Mercury Poisoning and Depression

Abraham Lincoln and His Little Blue Pills
Did Lincoln Suffer from Mercury Poisoning?

By Melissa Lee Phillips
Neuroscience for Kids Consultant
July 10, 2002
In the years before he became president, Abraham Lincoln exhibited many behaviors inconsistent with his dignified image. According to writings of some of his friends and acquaintances, Lincoln was prone to highly unpredictable moodiness, to fits of extreme rage, and to unexplained bizarre actions. Most of these behaviors stopped soon after his inauguration. Researchers, led by medical historian and retired physician Norbert Hirschhorn, published a report in 2001 hypothesizing that Lincoln suffered from mercury poisoning for years prior to his presidency.
For many years, Lincoln took pills referred to as "blue mass." The main ingredient in blue mass was elemental mercury. In the 1800s, these blue pills were commonly prescribed for a wide variety of conditions, including worms, tuberculosis, toothaches, and cholera. They also were often prescribed for "hypochondriasis," a very general medical term that was used to describe many different physical and mental problems. Lincoln was said to have suffered from one condition often attributed to hypochondriasis: melancholia or depression. It is likely that a physician recommended that Lincoln take these blue pills for his depression.
Physicians in the 1800s did not know that mercury is a powerful neurotoxin. Once ingested, mercury binds to molecules in the central nervous system and can cause behavioral problems. Common symptoms of mercury poisoning are irritability, anxiety, hostility, depression, insomnia, memory loss, nerve damage, tremor, and problems with dexterity. Lincoln apparently suffered many of these symptoms during the time he is believed to have taken mercury pills.
Dr. Hirschhorn and his colleagues wanted to know approximately how much mercury Lincoln's body would have absorbed when he took blue mass. They recreated some of these pills using a common 19th-century recipe. Using a mortar and pestle (with modern safety precautions to protect themselves from inhaling mercury vapors), they combined the ingredients used to make blue mass: mercury, licorice root, rosewater, honey, sugar, and dead rose petals. Next, they crushed the pills in an acidic solution similar to the acid present in the stomach. The solution was then run through a filter designed to imitate the membrane of the intestinal wall. They found that for each blue pill, about 750 micrograms of mercury would be absorbed into the body. The U.S. Environmental Protection Agency states that adults should consume no more than 21 micrograms of mercury in one day. A person who took the recommended dosage of two or three pills per day would be at significant risk for mercury poisoning.
Fortunately, many of the toxic effects of mercury are reversible. If mercury consumption stops, eventually some of the adverse symptoms stop too. A friend of Lincoln's wrote that Lincoln stopped taking blue pills about five months after the presidential inauguration. Lincoln felt that the pills made him "cross." After that, Lincoln's behavior changed: the rage attacks ceased, he remained calm in stressful situations, and the deep melancholy seemed to subside.
Hirschhorn and the other researchers point out some uncertainties in their conclusions. First, most of the written evidence for Lincoln's strange behaviors came from just one person. Second, no one knows how many years Lincoln took the blue pills. It is also unclear exactly how much mercury he consumed or precisely how much was absorbed into his bloodstream.
In spite of these unanswered questions, mercury poisoning seems likely to have affected part of Abraham Lincoln's life. It is relatively certain that he consumed mercury for many years and many of his reported behaviors are consistent with the neurobehavioral effects of mercury poisoning. This possibility of mercury poisoning could generate new insight into Lincoln's life and his influence on the history of the United States. It seems incredibly fortunate that he recognized the pills' ill effects and stopped taking them before the difficult years of his presidency.

For references and more information, see:

Hirschhorn, N., Feldman, R.G., and Greaves, I.A. Abraham Lincoln's Blue Pills, Perspectives in Biology and Medicine, 44 (Summer 2001): 315-32.

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