Over the years, factory bosses, doctors, labour leaders and everyday observers have speculated about the reasons behind mass fainting, a phenomenon prevalent in Cambodia in which groups of female factory workers swoon simultaneously.

Some have blamed cramped working conditions, overheating and a lack of ventilation, while others have noted that garment factory workers, who currently earn a minimum of $153 each month, are often undernourished and exhausted. Last year, a Chinese factory owner said workers were fainting because they had expended too much energy during wedding season revelry. Locals, however, will sooner blame angry ghosts and possession by evil spirits, who they believe have cursed the factories as retribution for some misdeed.

But new ethnographic research published in the peer-reviewed journal Transcultural Psychiatry has found a common thread – psychological trauma and fear – among mass fainting incidents in 34 garment factories between 2010 and 2015.

According to researcher and Monash University professor Maurice Eisenbruch, mass fainting should be considered within the context of social strife and the country’s bloody history of Khmer Rouge terror and violence.

“Mass fainting tended to break out in factories built on sites that were said to be blighted as killing fields, or in situations where there was conflict related to factory politics,” Eisenbruch writes. “Groups of workers seemed to be predisposed to faint when in a heightened state of fear or a climate of incipient dissent.”

During his study, Eisenbruch reviewed factories that had experienced at least one mass fainting. Moments of intense fear and vulnerability preceded all of the episodes, the study found.

“A mass fainting episode began with workers feeling afraid and becoming so terrified that they experienced momentary stupefaction and lapses of attention, feeling as if they had ‘lost their mind’,” Eisenbruch wrote. “Some older women had flashbacks to childhood experiences during the Khmer Rouge years, re-experiencing the terror that they would be the next to be executed.”

The fainters often experienced chest pain, palpitations and trembling, and disorientation.

Generally, the episodes were believed to have been brought on by specific events linked to local history and belief. In some cases, for example, foreign owners had constructed the factories on top of sites believed to be possessed by spirits or where mass executions or violence had taken place.

“Land-grabbing developers brought in bulldozers to demolish homes, including those of the guardian spirits, and people believed that failure to seek their permission led to outbreaks of mass fainting,” Eisenbruch noted.

He also found that conflict between foreign factory owners, local workers and labour leaders contributed to mass fainting, as did fatal industrial accidents and work-related suicides.

Ken Loo, a spokesman for the Garment Manufacturers Association in Cambodia, refuted the idea that stress was the main cause of fainting. Instead, he said low blood-sugar levels and the poor physical constitution of the workers are to blame.

Meanwhile, Ros Sopeaph, director of the organisation Gender and Development for Cambodia, said mass fainting can be stopped by ensuring healthy work environments for women.

“In the factories there are many chemicals. But the men are managers, and they are not sitting in the dust and chemicals and heat,” Sopeaph said. “We need to look at the air circulation and whether the women are sitting or standing or allowed to go to the bathroom.”

The number of workers who fainted in factories fell to 1,160 last year from 1,806 in 2015.

Mass fainting isn’t an exclusively Cambodian phenomenon. It has taken place in refugee camps in Nepal and schoolhouses in Colombia. In each location, large groups of women share close quarters in stressful conditions.

According to Eisenbruch, his ethnographic research demonstrates that mass fainting is a form of collective angst.

“For the affected women, the faint is the coming together in one moment of all that she has suffered in her life so far,” Eisenbruch wrote. “Terror, flashbacks, abuse, pain, powerlessness, vulnerability, injustice, poverty and endless grief and loss.”