Drapetomania was a supposed mental illness suffered by many American slaves in the 1800s. The word drapetomania comes from the Greek words drapetes, meaning 'a runaway' and -mania, meaning 'madness', and it meant just that -- the madness possessing slaves that made them want to run away from the slaveholders.
"The cause in the most of cases, that induces the negro to run away from service, is as much a disease of the mind as any other species of mental alienation, and much more curable, as a general rule. With the advantages of proper medical advice, strictly followed, this troublesome practice that many negroes have of running away, can be almost entirely prevented, although the slaves be located on the borders of a free state, within a stone's throw of the abolitionists."
The American doctor Samuel Cartwright published a short article in on this condition in DeBow's Review in 1851 (DeBow's was a popular agricultural, commercial, and industrial magazine in the American South at the time). He described it as if it were a medical condition, although the language and logic of the article was anything but scientific by today's standards. He explained that if the slave master provided food, shelter, and protection for his ward, by the law laid down in the Bible it was clear that any sane negro would be "spellbound", and remain in happy bondage, as that was his true role in the natural order of things. This was somewhat nutty even by the standards of the day (although not nearly as nutty as it sounds today). This article would likely not have gained any attention if the Southern states were not so highly motivated to justify their possession of slaves. As it was, the article was widely reprinted and was formally presented before Medical Association of Louisiana as a serious medical condition.
So what was the proper treatment for the insane escape artist? Before I tell you, I would like to assure you that This Is True. I am not making this up, nor exaggerating. The doctor's advice, in his own words and in all seriousness, was to use a traditional folk remedy which he labeled "whipping the devil out of them".
Now, before you get too worked up, Dr. Cartwright was against unnecessary cruelty to slaves. He found that the two ways that a slave owner might lose his slaves were either by treating them as equals or treating them cruelly, and he was against both of these errors in good housekeeping. You really should only whip your slaves if they are "sulky and dissatisfied without cause" or if they "raise their heads to a level with their master or overseer".
"If treated kindly, well fed and clothed, with fuel enough to keep a small fire burning all night--separated into families, each family having its own house--not permitted to run about at night to visit their neighbors, to receive visits or use intoxicating liquors, and not overworked or exposed too much to the weather, they are very easily governed--more so than any other people in the world."
Drapetomania is often used as an example of how science is misused and abused to support the ideals of the time, to show how certain behaviors can be treated as disease even when they clearly are not (sometimes, for example, to make a point about society's attitudes towards homosexuality or other marginalized proclivities), or just to give an example of how bloody stupid our forbearers were. It is no longer an accepted diagnosis, and has not been for many decades.
The full text of the article that appeared in DeBow's Review is available here. Be warned, it will raise your blood pressure.