Beleaguered celebrity Mel Gibson admitted in an affidavit that he slapped Oksana Grigorieva, the mother of his child. Gibson claims that Grigorieva was behaving hysterically while holding their baby in her arms. Out of concern for the child’s safety, he slapped Grigorieva to “bring her back to reality.” Is it wise to slap a hysterical person?

Absolutely not. Most psychiatrists avoid the word hysteria, because it’s loaded with sexist baggage from the 19th century. (More on that below.) It’s also poorly defined, since what a layperson might describe as hysterical behavior can have any number of causes. Otherwise healthy persons may behave erratically in stressful situations, but a panic attack may also signal the beginning of a conversion disorder—when psychological stress causes physical symptoms such as loss of coordination, hallucinations, or imperviousness to pain. (These symptoms usually dissipate in a few weeks.) In rare cases, hysteria can indicate a serious underlying disorder like psychosis. No matter what the cause of a given episode, however, a slap won’t improve matters. On the contrary, it will likely only amplify the sufferer’s chaotic mental state, confirm his or her feelings of fear or paranoia, and possibly provoke counter-aggression. If Gibson truly thought that either Grigorieva or his child were in immediate physical danger, the best response would have been to restrain the mother and call 911. Otherwise, he should have soothed her by encouraging her to relax, take a few deep breaths, and sit down.

Slapping was a common response to so-called hysterical episodes in the 19th century. At that time, almost all women suffering from psychological problems like hallucinations, convulsions, sleep-walking, unexplained pains, or amnesia were diagnosed with some form of “hysteria,” but researchers couldn’t agree on what caused it. Some blamed syphilitic parents, others pointed to imbalances in the blood, and many just thought the women were faking illness to avoid their domestic obligations. Psychologists slapped their patients in the face, doused them with water, or suffocated them to snap them out of their stupors. An American physician named Silas Weir Mitchell put his patients in isolation and stuffed them with food until they gained 50 pounds. His theory was that the women would find their home lives joyous after escaping the treatment.

Face-slap therapy didn’t die completely in the 19th century. As recently as the 1980s, some doctors believed that slapping a patient in the face or dousing him with water could stop an absence seizure—that’s when a person stares blankly into space. But doctors don’t really use the tactic anymore and strongly discourage laypeople from trying it.

It’s not surprising that a Hollywood lifer like Gibson would try the slap technique, an old movie standby. Cher slaps a love-sick Nicholas Cage in Moonstruck, exhorting him to “snap out of it.” Frank Langella slaps a hysterical Leslie-Ann Down in the 1981 thriller Sphinx. And in the animated film The Incredibles, Edna Mode slaps a dazed Elastigirl after the latter finds out her husband has been doing covert superhero work. * Slapping someone back to sanity—usually while yelling something like “Get ahold of yourself!”—is such a venerable film tradition that it was parodied in the movie Airplane!.

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Explainer thanks Philip R. Muskin of Columbia University Medical Center.Like Slate and the Explainer on Facebook. Follow us on Twitter.

Correction, Nov. 18, 2010: This article originally misspelled Edna Mode’s last name Mole. ( Return to the corrected sentence.)

* Correction, Nov. 18, 2010: A headline for this article originally called Oksana Grigorieva Mel Gibson’s wife. They were not married.