It all began with a frantic phone call on August 31, 1944. 

With a (then) population of only 16,000 people, Mattoon, Illinois was a fairly quiet town and police were rarely called in for more than routine cases. When Mrs. Bert Keaney reported that she and other members of her family had been attacked in their home, police were quick to respond. In her statement, Mrs. Keaney reported that she had noticed a prowler lurking in the shadows near the house. The intruder then opened a bedroom window and sprayed something that left a "sickening, sweet odor". Although she first thought that the smell was coming from the flowers outside, she noticed that the smell was getting stronger and that then began feeling paralysed in the lower part of her body. Police found no trace of any intruder and Mrs. Kearne experienced no lingering symptoms after becoming aware of the strange gas. When her husband returned home later that evening, he noticed a prowler "dressed in dark clothing and wearing a tight fitting cap" lurking at a window. When the prowler who managed to escape after he tried to chase him, police were called again. No trace of any prowler was found after a careful search of the neighbourhood.

That same night, another woman living nearby reported a similar incident. After being awakened by the sound of her young daughter coughing, she found herself paralysed and was unable to get out of her bed to check. Another couple also reported being awakened by a nauseating gas smell and feeling paralysed (the actual order in which the different incidents occurred varies depending on which source you consult).  

The local newspaper, the Mattoon Daily Journal-Gazette, published a sensational story describing the Kearney incident with the headline: "Anaesthetic Prowler on the Loose". Along with describing the reported symptoms, the newspaper story speculated on the type of anaesthetic that had been sprayed into the house (chloroform or ether were particularly favored). Robbery was given as the prowler's likely motive for targeting the house (the story also mentioned that there had been a considerable amount of money in the house at the time). Over the course of nine days after the story was published, more than twenty-five incidents involving twenty-seven women and two men were reported to the police. All of the complainants described being sprayed with an unknown gas. The symptoms they described included: burning mouth sensations, nausea, vomiting, palpitations, and difficulty walking.

Various newspapers across the country picked up on the story which only reinforced the hysteria. In a Chicago Herald-American story published on September 10, readers were told that:

Groggy as Londoners under protracted aerial blitzing, this town's bewildered citizens reeled today under the repeated attacks of a mad anesthetist who has sprayed a deadly nerve gas into 13 homes and has knocked out 27 victims. Seventy others dashing to the area in response to the alarm, fell under the influence of the gas last night. All skepticism has vanished and Mattoon grimly concedes it must fight haphazardly against a demented phantom adversary who has been seen only fleetingly and so far has evaded traps laid by city and state police and posses of townsmen.  

As the "Mad Gasser" hysteria spread, many Mattoon citizens armed themselves with shotguns and stood guard on their doorsteps. Some even claimed to have spotted him and heard the sound of his spray-gun being pumped. Since local police felt overwhelmed, they called in state police with radio-equipped squad cars and toxicological experts to test affected houses. Police also began checking the records of all recently released inmates from prisons and mental hospitals. While police noted various inconsistencies in the stories they were given (watch dogs at several of the houses failed to bark despite the presumed presence of an intruder), they were still obliged to investigate. Authorities were also obliged to put a request in the local paper asking for the "roving bands of men and boys" to disband and that guns be put away "because some innocent person might get killed".

 After ten days, nothing further occurred and no real clues were found. Newspapers soon moved on to other news events and embarrassed local residents tried to get on with their lives. Police and newspapers began to attribute the entire episode to mass hysteria and the Mad Gasser epidemic was officially over. The victims themselves were slow to accept the possibility that they had been deceived, but they had little choice given the lack of any real evidence to support their claims. Despite the Mad Gasser episode being short-lived, social scientists began to take a serious look at why it happened.  

The first in-depth analysis of the epidemic was by Donald Johnson of the University of Illinois. His now-classic paper titled The Phantom Anesthetist of Mattoon: A Field Study of Mass Hysteria was published in a 1945 issue of the Journal of Abnormal and Social Psychology. In the paper, Johnson carefully reviewed Mattoon police records and interviewed gas attack victims. He noted the sharp rise in "gasser" calls after the first news story and the even sharper drop after the first few days (although "prowler" calls continued for some time afterward). He also consulted professional chemists who pointed out that no gas would have characteristics  that matched all of the different symptoms reported.

In studying the demographics of the gasser victims, Johnson noted that 93 per cent of them were women (as opposed to 52 per cent of the general Mattoon population). Most of the victims had only a grade school education and came from a relatively low socioeconomic background. None of the attacks occurred in Mattoon's high-income areas. After comparing the gasser victims to the subjects in Hadley Cantril's research study into the War of the Worlds panic, Johnson argued that better educated people are less susceptible to suggestibility and more likely to investigate unusual claims. 

Johnson also investigated how the victims first heard about the "gasser" in the first place and quickly established that most of them had learned of it through the local newspaper. Since the Mattoon Daily Journal-Gazette was the main source of information for most Mattoon families (this was before television and the Internet), its psychological influence in shaping the "gasser" hysteria was considerable. This was especially apparent considering the alarmist tone that the newspaper adopted in covering the attacks. Stories with headlines such as "Mad Anesthetist Strikes Again" would hardly reassure Mattoon's residents.

The Mad Gasser epidemic largely subsided when the Gazette began to lose interest in the story. A grudging editorial on September 20 acknowledged the possibility of mass hysteria (despite suggesting that there might have been a physical basis for the strange odours). National newspapers that had reported on the epidemic quickly embraced the mass hysteria explanation as well. In his study, Johnson concluded that the entire episode had been psychogenic in nature.  

Throughout history, there have been numerous incidents of mass hysteria involving everything from demonic possession to environmental hazards. While the duration and extent of the hysteria tends to vary, there are certain common factors which include: victims who are often relatively disenfranchised (typically women, children, or vulnerable minorities), a trusted means of exchanging information (word of mouth or local media), and a credible threat. Once the panic sets in, attempts at alleviating fears by government sources are often counterproductive. In the case of the Mattoon Mad Gasser, time and lack of new incidents caused the panic to die down relatively quickly (and before anyone was killed by one of the armed gangs). Still, as a case study in mass hysteria, the Mattoon epidemic is a useful example in how quickly fear can arise and how easy it is to spin out of control.


Dr. Vitelli is a practicing psychologist from Hamilton, Ontario, Canada. He also writes "Providentia" (, a blog about psychology in today's world.


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