In March 2011, the Journal made an error—on the cover. It portrayed a short, smooth, and vertical staff with two intertwined snakes, the Caduceus, as the ancient symbol of medicine (above left). Four months later, a letter to the editor (1) pointed out that the correct symbol is instead the diagonal, rough-hewn, single-snaked staff of Asclepius (above right). This mistake began in the late 19th century. One of the earliest medical misuses of the Caduceus was by John Churchill, a London publisher of medical books (2). American publishers followed, and in 1902 the U.S. Army Medical Corps adopted the Caduceus as its insignia. Many others, including the U.S. Public Health Service, were to follow. Corrections seem to have had little effect. In fact, in reviewing the history of this error, we found more than 30 articles in the literature that discuss the mistaken use of the Caduceus instead of the staff of Asclepius. This discussion dates back to a 1928 article in the Canadian Medical Association Journal that describes the history and inaccurate swapping of these two symbols (3).

Yet, 83 years later, the American Journal of Psychiatry repeated the same error. At least we are in good company. In 2003, an article in the Annals of Internal Medicine explored the historical origin of these two symbols (4), and the many letters to the editor that followed suggested that the debate remained heated. As psychiatrists, we can contribute to the dialogue by speculating not on the error itself but instead on the meaning of a mistake that persists in spite of correction. After all, isn't the understanding of repeated errors one of our primary skills?

Named as the god of medicine by the ancient Greeks, Asclepius inherited his healing powers from his father Apollo, and he carried a staff entwined with only one serpent. He represents the medical tradition of serving the vulnerable, as he was a caretaker of slaves and other victims of persecution. In contrast, the Caduceus was carried by Hermes, a messenger of the Greek gods who was a strikingly different character. As Zeus's son, Hermes was a patron of merchants.

There are several explanations of why snakes came to be associated with both Asclepius and Hermes. In one, Asclepius kills a snake. A second snake arrives and feeds herbs to the first one, reviving it. Asclepius observes this and uses the same medicinal herbs to revive a dead man. A second myth, about the Caduceus, describes how Hermes encountered two serpents engaged in combat. He separated them with his wand, thus ending the battle. Consequently, they joined in his staff as a symbol for the power to resolve disputes peacefully. Thus, snakes are linked with both reviving the dead and resolving disputes.

In this day and age, it seems significant to mistake the symbol of commerce with that of medicine, as these two communities have unfortunately become enmeshed. Another interpretation may be less profound: are two symmetrical snakes around a staff easier to draw than one? Asclepius is named in the opening lines of the Hippocratic Oath. As physicians, we must first do no harm and then do our best to learn from our mistakes. Now that the Caduceus has survived more than a century as the erroneous medical symbol, who is to say that it is still a mistake? Perhaps our task, as psychiatrists, is not to correct this error once again, but to study the reasons for its persistence.