Hardly. It's been almost 50 years since girls at a boarding school in Tanganyika (now Tanzania) were struck by an illness whose symptoms — fainting, nausea and helpless laughter — soon spread to other communities. Or consider the Pokémon contagion in 1997, when 12,000 Japanese children experienced fits, nausea and shortness of breath after watching a television cartoon. Sufferers of World Trade Center syndrome, meanwhile, blamed proximity to Ground Zero for coughs and other respiratory problems long after airborne contaminants posed any health threat.
All these are examples of mass hysteria, a bizarre yet surprisingly common phenomenon that is increasingly recognized as a significant health and social problem. For centuries it has crossed cultures and religions, taking on different forms to keep pace with popular obsessions and fears. In our post-9/11 world, it thrives on the anxiety caused by terrorist attacks, nuclear radiation and environmental gloom. "At any one time there are probably hundreds of episodes happening all around the world," says Simon Wessely, a psychology professor at the Institute of Psychiatry at King's College London. "They just don't normally get reported."
While New York City firefighters and Tokyo schoolchildren have both succumbed to what experts categorize as a mass sociogenic or psychogenic illness, young women are particularly vulnerable — and in Cambodia they make up most of the garment industry's 350,000-strong workforce. Conditions for workers have improved over the years, says the ILO, but few would envy their lot. Women leave their villages to toil in suburban factories for long hours and low pay, often making products for famous Western brands such as Puma and H&M. They live in grim communal shacks, eating sparingly so that they can send as much money as possible back to their homes.
(Read about the burden of good intentions in manufacturing.)
"Stress, boredom, concern about their children and other factors among young females could trigger psychogenic fainting or other illnesses," says Ruth Engs, a professor of applied health sciences at Indiana University who investigated an outbreak of mass hysteria at a Midwestern university in 1995 after false reports of a toxic leak caused dozens of people to fall ill. "Poor ventilation, few breaks, stress from piecework production and other workplace conditions would all be contributing factors."
There have been dozens of similar episodes in Cambodian factories since the garment industry began rapidly expanding in the late 1990s. The recent incidents involved groups of up to 80 workers at a time, but the women didn't actually faint. "They don't lose consciousness," says Tuomo Poutiainen, chief technical adviser for Better Factories Cambodia, an ILO program seeking to improve factory working conditions. "They become powerless and lie down, and that's repeated by some co-workers."
This is unwise, says Wessely, who has studied cases of mass hysteria dating back to the Middle Ages. In previous centuries, reports of mass hysteria were common in European convents. Forced to join by their elders, young women endured hunger, boredom, isolation and beatings. They rebelled against these harsh regimes with behavior that at the time was attributed to demonic possession. They had fits, ripped off their veils, swore and blasphemed, exposed their private parts and meowed like cats. Some nuns were branded witches and beheaded or burned at the stake.
Such episodes weren't confined to Christian institutions in days of yore. In Malaysia in 1987, a number of Muslim girls took hostages at knifepoint at their oppressive religious school in Kedah state. This act of desperation followed a series of "crying fits, screaming, abnormal movements, possession states and histrionics," according to a 2002 academic paper co-written by Wessely and Australian sociologist Robert E. Bartholomew. Factories have also been fertile grounds for mass hysteria. The first recorded outbreak occurred at a cotton mill in Lancashire, England, in 1787, when 24 workers — all but one of them female — violently convulsed and reported feeling suffocated, according to the academics' report. Similar episodes were reported in France, Germany, Italy and Russia, but their numbers declined in the 20th century as unions gained power and workers' health and safety conditions improved.
For the past century, episodes of mass hysteria have been dominated by reports of strange odors and fears of toxic gases. In the 1930s and '40s, dozens of people in Virginia and Illinois reported being attacked by "mad gassers" who released toxic fumes into their homes; the odors were later found to have been caused by such mundane things as blocked chimneys and flatulence. Then came Sept. 11. The terrible events of that day, and the anthrax attacks that followed, caused profound anxiety about terrorism. There were thousands of anthrax false alarms in October alone, in which the reported symptoms were hard to distinguish from those of a real attack.
(Read about China's rising production costs.)
An abnormal odor is now the trigger "in nearly all episodes of acute mass hysteria," Wessely says. In Cambodia, a bad smell was reported at a factory that makes clothing for H&M before some 200 workers collapsed in two separate incidents in August. But investigations by Cambodian officials, the ILO and H&M "have not found any plausible causes so far," H&M said in a statement. "The workers' health, well-being and safety are of importance to us and we [will] do all we can to find the root causes of the incidents." It dismissed a diagnosis of mass hysteria as "speculating."
ILO experts might yet discover a cause that rules out mass hysteria. (In the 1980s, Puerto Rican garment workers diagnosed with hysteria were later found to have been poisoned.) Nevertheless, a decade of unsolved mass faintings reflects unfavorably on Cambodia's garment industry and the famous Western companies it supplies. "This is a wake-up call for the industry to pay more attention to the well-being of the workers," Poutiainen says. "At the end of the day, they have given a lot to Cambodia."
See photos of Chinese workers.
After medical checks and rest, the women returned to work, with no apparent ill effects. "The good thing is none of the workers has a serious medical condition," Poutiainen says. "But it's also troubling because employers and managers can't get to the root cause." He admits that "some kind of mass-hysteria element" might be involved, but adds that the ILO wants first to eliminate other factors. Its investigative team includes experts in health and safety, industrial hygiene and nutrition — but not in behavioral psychology.
(Read about China's at-risk factories.) 
