--- title: 5 Strange Cases of Mass Hysteria description: "The dictionary definition of the phenomenon known as mass hysteria is: \"a condition affecting a group of persons, characterized by excitement or anxiety, irrational behavior or beliefs, or inexplicable symptoms of illness.\"\n\nInstances of mass hysteria have been recorded throughout human history and across the whole world. While it can't be predicted when it might happen, there do seem to be similar underlying factors between cases which can explain why an epidemic might start, if not exactly how. The common link seems to be a group of people under stressful conditions that manifest their psychological stress into physical symptoms. These symptoms are then passed throughout the group they are in with everyone falling prey to the strange behaviour or beliefs. There are some very famous examples, such as the Salem Witch Trials and the Satanic Panic of the 1980s and 90s that have taken mass hysteria and irrational beliefs to deadly lengths. Let's look at some more of the weirdest cases of mass hysteria that have been recorded so far.\n\n## The Dancing Plague\n\nOne person deciding to behave a bit oddly is not usually a cause for concern; if you see someone dancing around by themselves in the middle of a city street you generally give them a wide berth and get on with your day. But what if other people started joining in and not in a fun flashmob kind of way but in an uncontrolled and fervent way that went on for days and led to some people dying? That's what happened in Strasbourg in 1518. You might have heard of \"St Vitus Dance\", a disorder where people start uncontrollably jerking and moving. This was named after St. Vitus, obviously, who was the patron saint of dancers and entertainers. There isn't anything entertaining about this dance, though, with some sufferers eventually dying of exhaustion or heart attacks. In one of the earliest documented examples of mass hysteria, a woman started dancing in the street in July, 1518. After a while, other people joined her and the dancing group grew as the outbreak spread. Incredibly, it wasn't until September that the dancing plague was brought under control with doctors rounding up people to take them off to hospital and the magistrate of Strasbourg clamping down on this sort of behaviour. At the time, a theory of demonic possession was offered as a reason for the dancing and, as most of the afflicted were young women, another suggestion was given as \"overheated blood\". There are no confirmed numbers relating to how large the afflicted group was, with estimates ranging between 50 and a whopping 400 but even 50 people unable to stop dancing is 50 too many. Another theory proffered to explain the behaviour is that of the victims having ingested a fungus on mouldy bread which acts in a similar way to LSD. It does not explain why everyone behaved so similarly, though, as psychotropic chemicals do not affect large numbers of people in the same way. Mass hysteria seems more likely with the underlying factor being the stress caused by the poor conditions many people were living in at the time. There were many recorded outbreaks of this dancing disease, especially in the Middle Ages, with the issue generally resolving itself after weeks or sometimes months. It does still sometimes occur nowadays and medication can be given to help control the involuntary movements but no medical cure has been found.\n\n## Strange Events at the Nunnery\n\nYou wouldn't expect too many weird things to be afoot in a nunnery, right? They are calm groups of religious women living under God and serving their communities. Well, in the Middle Ages, two very bizarre cases of mass hysteria took hold of convents across Europe. The first example happened in France where one young nun started to make meowing noises, as one does. This escalated into every nun in the convent meowing at the same time for hours a day. It might not have been so bad if they'd chosen a different animal to imitate but cats were linked with Satan at the time so not only were the women making annoying noises, they were also baiting God by sounding like the devil's pet. Eventually this all stopped when, after complaints from the neighbours, a group of soldiers arrived and threatened to beat the nuns if they didn't put a sock in it.\n\nLater in the fifteenth century, a nun in a German convent began to bite her sisters. Instead of being put in a nun time-out or thrown in an insane asylum, the biting behaviour actually spread, with all the nuns in the convent taking a chomp at each other on a regular basis. As if this wasn't weird enough, when news of this peculiar social contagion spread, it started happening at other nunneries across Germany, into Holland and even as far as Italy. With no clue as to what to do, religious authorities tried praying and eventually turned to exorcisms to cast the biting demons out but this did nothing to prevent the epidemic from continuing. Finally, it came down to physical threats and punishments of whipping or being held under water that got the behaviour to stop. You might wonder why nuns were seemingly so susceptible to falling victim to mass hysteria but, especially at this time in history, lots of the convents were made up of young women put there against their will, forced into a life of celibacy and hard work by their families. If this doesn't create a breeding ground for psychological stress then I don't know what does. Also, the middle ages were a very religious and superstitious time which would have fed into the bizarre group events with talk of devils and sorcery adding fuel to the fire.\n\n## The Halifax Slasher\n\nFear can make people do strange things. In Halifax, England in November 1938, the whole town was in a panic after a number of attacks by a mysterious man who was slashing people with a razor. Encouraged by scaremongering newspaper articles, mass hysteria gripped the town with businesses shutting down until the attacker was found. More reports came in from neighbouring towns of Slasher attacks and detectives from Scotland Yard were eventually called in to investigate. Convinced they were doing the right thing, groups of townspeople started roaming the streets to find the Slasher, themselves becoming violent attackers if they came upon a person who was in the wrong place at the wrong time.\n\nAfter just over two weeks of the town becoming a hotbed of suspicion, violence and paranoia, one of the first Slasher victims fessed up that his injuries had, in fact, been self-inflicted. After this admission, it turned out that at least 9 of the 12 recorded victims had actually caused their injuries themselves and had not been attacked by a razor-wielding maniac. Four of these people ended up in jail for public mischief and Scotland Yard closed the case with the conclusion that there had never been a Slasher, it was all just a collective delusion.\n\n## The Laughing Epidemic\n\nWe've all heard that laughter is the best medicine but what happens when it's actually the disease? Maybe these quotes would be more accurate with Charles Dickens saying: \"There is nothing in the world so irresistibly contagious as laughter and good humor.\" And according to Mark Twain: \"Against the assault of laughter, nothing can stand.\" That brings us to 1962 and the Tanganyika Laughter Epidemic. In what is now Tanzania, a small group of young girls started giggling in their boarding school one day. Nothing unusual there, children laugh all the time. This proved to be different, however. After laughing fits lasting up to several hours, this laughter did prove to be contagious in the worst possible way. Soon, other girls had joined in and six weeks later, over half the school was laughing in prolonged, uncontrollable bursts and the establishment was shut down. Unfortunately, this didn't end the epidemic as the girls were still having outbursts at home and the contagion spread throughout their communities. If you're thinking that laughing so much doesn't seem that bad, you're wrong. It would be totally exhausting and they weren't laughing because they were happy. In fact, other symptoms of this mass hysteria were crying, rashes and fainting. The schools eventually reopened but the laughing epidemic was still going strong so they had to shut down again almost immediately. In total, over 1000 cases were reported and 14 schools were closed. It's believed that once again, stress and anxiety were the cause of the initial outbreak. The religious boarding school was not known for its easygoing, lenient nature and there was a lot of uncertainty in the country in general as Britain had ceased its rule only a few months earlier. It wasn't until over a year later that the laughter stopped, as abruptly as it had begun.\n\n## Recurrent Mass Hysteria\n\nThe only known case of a recurrent mass hysteria epidemic is in a school in western Nepal. Since the 1990s, the small country has seen many outbreaks of mass hysteria, usually presenting as young people crying and writhing on the ground but they have been isolated incidents. In August 2016, a young schoolgirl started shouting and having crying outbursts which quickly spread throughout her class, resulting in about 12 children demonstrating the same symptoms by the end of the day. The next year, the same thing happened again with 18 children being afflicted by group dissociative symptoms. And then it happened again in 2018, with 47 boys and girls displaying the same bizarre behaviour. It has been suggested that cases such as this might have an environmental trigger, some smell or chemical in the air, but a study of the 2018 phenomenon in the Nepalese school found nothing that could have acted on the children in this way. Once again it was put down to stress and anxiety which was then exacerbated by the attention the episodes received from local onlookers. Every year, once the affected children had been taken out of the school grounds, the symptoms resolved themselves pretty quickly. The outbreaks stopped after three years and no further cases have been reported.\n\n## Key Takeaways\n\n- Mass hysteria is characterized by irrational behavior or beliefs in a group under stress.\n- Historical cases of mass hysteria include the Dancing Plague in 1518 and the Tanganyika Laughter Epidemic in 1962.\n- Stressful conditions and psychological stress often manifest as physical symptoms in mass hysteria.\n- The Halifax Slasher incident in 1938 was revealed to be a collective delusion with self-inflicted injuries.\n- Recurrent mass hysteria in a Nepalese school was linked to stress and anxiety, resolving quickly when affected students were removed.\n\n## Frequently Asked Questions\n\n### What is mass hysteria?\n\nMass hysteria is a condition affecting a group of persons, characterized by excitement or anxiety, irrational behavior or beliefs, or inexplicable symptoms of illness.\n\n### What are some common factors underlying mass hysteria?\n\nMass hysteria often occurs in groups of people under stressful conditions who manifest their psychological stress into physical symptoms, which then spread throughout the group.\n\n### What was the Dancing Plague?\n\nThe Dancing Plague was an event in Strasbourg in 1518 where people started dancing uncontrollably in the streets, leading to some deaths from exhaustion or heart attacks. It was one of the earliest documented examples of mass hysteria.\n\n### What happened at the nunnery in France during the Middle Ages?\n\nIn a French nunnery, a young nun started making meowing noises, which escalated into all the nuns meowing together for hours a day. This behavior was eventually stopped when soldiers threatened to beat the nuns if they didn't stop.\n\n### What was the Halifax Slasher incident?\n\nIn Halifax, England in 1938, mass hysteria gripped the town after reports of a mysterious man slashing people with a razor. It turned out that most of the victims had self-inflicted their injuries, and there was never an actual Slasher.\n\n### What was the Tanganyika Laughter Epidemic?\n\nIn 1962, in what is now Tanzania, a group of young girls started giggling uncontrollably, and the laughter spread to over 1,000 people, leading to the closure of 14 schools. The epidemic lasted over a year.\n\n### What was the recurrent mass hysteria in Nepal?\n\nSince the 1990s, a school in western Nepal has experienced recurrent outbreaks of mass hysteria, with students crying and writhing on the ground. These outbreaks occurred annually from 2016 to 2018 and were attributed to stress and anxiety.\n\n### What are some theories about the cause of the Dancing Plague?\n\nTheories about the Dancing Plague include demonic possession, overheated blood, and ingestion of a fungus on mouldy bread acting like LSD. However, mass hysteria due to stress from poor living conditions is considered more likely.\n\n### Why were nuns particularly susceptible to mass hysteria in the Middle Ages?\n\nMany convents were made up of young women forced into a life of celibacy and hard work, creating a breeding ground for psychological stress. Additionally, the religious and superstitious nature of the time contributed to bizarre group events.\n\n### How was the Halifax Slasher incident resolved?\n\nThe Halifax Slasher incident was resolved when one of the first victims admitted to self-inflicting their injuries. It was found that at least 9 of the 12 recorded victims had caused their injuries themselves, leading to the conclusion that there had never been a Slasher.\n\n## Sources\n\n- [Original Side Projects video: 5 Strange Cases of Mass Hysteria](https://www.youtube.com/watch?v=BUA-ygKEodM)\n- [Hero image source](https://upload.wikimedia.org/wikipedia/commons/2/2f/UNICEF_Mitarbeiter_untersucht_Menschen_in_Aethiopien.jpg) by Nesbitt / openverse, by-sa.\n\n## Related Coverage" url: https://sideprojects.pub/article/5-strange-cases-of-mass-hysteria.md canonical: https://sideprojects.pub/article/5-strange-cases-of-mass-hysteria datePublished: 2026-07-02 dateModified: 2026-07-02 author: - name: Simon Whistler url: https://sideprojects.pub/author/simon-whistler publisher: Side Projects image: "https://media.sideprojects.pub/cdn-cgi/image/width=1600,height=900,fit=cover,quality=80,format=auto/articles/BUA-ygKEodM/hero.jpg" type: Article contentHash: eb4dc8725ee00a2ba0a1b4721a22bd6799a26ea107d12d78decb9d14a29136bd tokens: 3441 summaryUrl: https://sideprojects.pub/article/5-strange-cases-of-mass-hysteria.md.summary.md --- The dictionary definition of the phenomenon known as mass hysteria is: "a condition affecting a group of persons, characterized by excitement or anxiety, irrational behavior or beliefs, or inexplicable symptoms of illness." Instances of mass hysteria have been recorded throughout human history and across the whole world. While it can't be predicted when it might happen, there do seem to be similar underlying factors between cases which can explain why an epidemic might start, if not exactly how. The common link seems to be a group of people under stressful conditions that manifest their psychological stress into physical symptoms. These symptoms are then passed throughout the group they are in with everyone falling prey to the strange behaviour or beliefs. There are some very famous examples, such as the Salem Witch Trials and the Satanic Panic of the 1980s and 90s that have taken mass hysteria and irrational beliefs to deadly lengths. Let's look at some more of the weirdest cases of mass hysteria that have been recorded so far. ## The Dancing Plague One person deciding to behave a bit oddly is not usually a cause for concern; if you see someone dancing around by themselves in the middle of a city street you generally give them a wide berth and get on with your day. But what if other people started joining in and not in a fun flashmob kind of way but in an uncontrolled and fervent way that went on for days and led to some people dying? That's what happened in Strasbourg in 1518. You might have heard of "St Vitus Dance", a disorder where people start uncontrollably jerking and moving. This was named after St. Vitus, obviously, who was the patron saint of dancers and entertainers. There isn't anything entertaining about this dance, though, with some sufferers eventually dying of exhaustion or heart attacks. In one of the earliest documented examples of mass hysteria, a woman started dancing in the street in July, 1518. After a while, other people joined her and the dancing group grew as the outbreak spread. Incredibly, it wasn't until September that the dancing plague was brought under control with doctors rounding up people to take them off to hospital and the magistrate of Strasbourg clamping down on this sort of behaviour. At the time, a theory of demonic possession was offered as a reason for the dancing and, as most of the afflicted were young women, another suggestion was given as "overheated blood". There are no confirmed numbers relating to how large the afflicted group was, with estimates ranging between 50 and a whopping 400 but even 50 people unable to stop dancing is 50 too many. Another theory proffered to explain the behaviour is that of the victims having ingested a fungus on mouldy bread which acts in a similar way to LSD. It does not explain why everyone behaved so similarly, though, as psychotropic chemicals do not affect large numbers of people in the same way. Mass hysteria seems more likely with the underlying factor being the stress caused by the poor conditions many people were living in at the time. There were many recorded outbreaks of this dancing disease, especially in the Middle Ages, with the issue generally resolving itself after weeks or sometimes months. It does still sometimes occur nowadays and medication can be given to help control the involuntary movements but no medical cure has been found. ## Strange Events at the Nunnery You wouldn't expect too many weird things to be afoot in a nunnery, right? They are calm groups of religious women living under God and serving their communities. Well, in the Middle Ages, two very bizarre cases of mass hysteria took hold of convents across Europe. The first example happened in France where one young nun started to make meowing noises, as one does. This escalated into every nun in the convent meowing at the same time for hours a day. It might not have been so bad if they'd chosen a different animal to imitate but cats were linked with Satan at the time so not only were the women making annoying noises, they were also baiting God by sounding like the devil's pet. Eventually this all stopped when, after complaints from the neighbours, a group of soldiers arrived and threatened to beat the nuns if they didn't put a sock in it. Later in the fifteenth century, a nun in a German convent began to bite her sisters. Instead of being put in a nun time-out or thrown in an insane asylum, the biting behaviour actually spread, with all the nuns in the convent taking a chomp at each other on a regular basis. As if this wasn't weird enough, when news of this peculiar social contagion spread, it started happening at other nunneries across Germany, into Holland and even as far as Italy. With no clue as to what to do, religious authorities tried praying and eventually turned to exorcisms to cast the biting demons out but this did nothing to prevent the epidemic from continuing. Finally, it came down to physical threats and punishments of whipping or being held under water that got the behaviour to stop. You might wonder why nuns were seemingly so susceptible to falling victim to mass hysteria but, especially at this time in history, lots of the convents were made up of young women put there against their will, forced into a life of celibacy and hard work by their families. If this doesn't create a breeding ground for psychological stress then I don't know what does. Also, the middle ages were a very religious and superstitious time which would have fed into the bizarre group events with talk of devils and sorcery adding fuel to the fire. ## The Halifax Slasher Fear can make people do strange things. In Halifax, England in November 1938, the whole town was in a panic after a number of attacks by a mysterious man who was slashing people with a razor. Encouraged by scaremongering newspaper articles, mass hysteria gripped the town with businesses shutting down until the attacker was found. More reports came in from neighbouring towns of Slasher attacks and detectives from Scotland Yard were eventually called in to investigate. Convinced they were doing the right thing, groups of townspeople started roaming the streets to find the Slasher, themselves becoming violent attackers if they came upon a person who was in the wrong place at the wrong time. After just over two weeks of the town becoming a hotbed of suspicion, violence and paranoia, one of the first Slasher victims fessed up that his injuries had, in fact, been self-inflicted. After this admission, it turned out that at least 9 of the 12 recorded victims had actually caused their injuries themselves and had not been attacked by a razor-wielding maniac. Four of these people ended up in jail for public mischief and Scotland Yard closed the case with the conclusion that there had never been a Slasher, it was all just a collective delusion. ## The Laughing Epidemic We've all heard that laughter is the best medicine but what happens when it's actually the disease? Maybe these quotes would be more accurate with Charles Dickens saying: "There is nothing in the world so irresistibly contagious as laughter and good humor." And according to Mark Twain: "Against the assault of laughter, nothing can stand." That brings us to 1962 and the Tanganyika Laughter Epidemic. In what is now Tanzania, a small group of young girls started giggling in their boarding school one day. Nothing unusual there, children laugh all the time. This proved to be different, however. After laughing fits lasting up to several hours, this laughter did prove to be contagious in the worst possible way. Soon, other girls had joined in and six weeks later, over half the school was laughing in prolonged, uncontrollable bursts and the establishment was shut down. Unfortunately, this didn't end the epidemic as the girls were still having outbursts at home and the contagion spread throughout their communities. If you're thinking that laughing so much doesn't seem that bad, you're wrong. It would be totally exhausting and they weren't laughing because they were happy. In fact, other symptoms of this mass hysteria were crying, rashes and fainting. The schools eventually reopened but the laughing epidemic was still going strong so they had to shut down again almost immediately. In total, over 1000 cases were reported and 14 schools were closed. It's believed that once again, stress and anxiety were the cause of the initial outbreak. The religious boarding school was not known for its easygoing, lenient nature and there was a lot of uncertainty in the country in general as Britain had ceased its rule only a few months earlier. It wasn't until over a year later that the laughter stopped, as abruptly as it had begun. ## Recurrent Mass Hysteria The only known case of a recurrent mass hysteria epidemic is in a school in western Nepal. Since the 1990s, the small country has seen many outbreaks of mass hysteria, usually presenting as young people crying and writhing on the ground but they have been isolated incidents. In August 2016, a young schoolgirl started shouting and having crying outbursts which quickly spread throughout her class, resulting in about 12 children demonstrating the same symptoms by the end of the day. The next year, the same thing happened again with 18 children being afflicted by group dissociative symptoms. And then it happened again in 2018, with 47 boys and girls displaying the same bizarre behaviour. It has been suggested that cases such as this might have an environmental trigger, some smell or chemical in the air, but a study of the 2018 phenomenon in the Nepalese school found nothing that could have acted on the children in this way. Once again it was put down to stress and anxiety which was then exacerbated by the attention the episodes received from local onlookers. Every year, once the affected children had been taken out of the school grounds, the symptoms resolved themselves pretty quickly. The outbreaks stopped after three years and no further cases have been reported. ## Key Takeaways - Mass hysteria is characterized by irrational behavior or beliefs in a group under stress. - Historical cases of mass hysteria include the Dancing Plague in 1518 and the Tanganyika Laughter Epidemic in 1962. - Stressful conditions and psychological stress often manifest as physical symptoms in mass hysteria. - The Halifax Slasher incident in 1938 was revealed to be a collective delusion with self-inflicted injuries. - Recurrent mass hysteria in a Nepalese school was linked to stress and anxiety, resolving quickly when affected students were removed. ## Frequently Asked Questions ### What is mass hysteria? Mass hysteria is a condition affecting a group of persons, characterized by excitement or anxiety, irrational behavior or beliefs, or inexplicable symptoms of illness. ### What are some common factors underlying mass hysteria? Mass hysteria often occurs in groups of people under stressful conditions who manifest their psychological stress into physical symptoms, which then spread throughout the group. ### What was the Dancing Plague? The Dancing Plague was an event in Strasbourg in 1518 where people started dancing uncontrollably in the streets, leading to some deaths from exhaustion or heart attacks. It was one of the earliest documented examples of mass hysteria. ### What happened at the nunnery in France during the Middle Ages? In a French nunnery, a young nun started making meowing noises, which escalated into all the nuns meowing together for hours a day. This behavior was eventually stopped when soldiers threatened to beat the nuns if they didn't stop. ### What was the Halifax Slasher incident? In Halifax, England in 1938, mass hysteria gripped the town after reports of a mysterious man slashing people with a razor. It turned out that most of the victims had self-inflicted their injuries, and there was never an actual Slasher. ### What was the Tanganyika Laughter Epidemic? In 1962, in what is now Tanzania, a group of young girls started giggling uncontrollably, and the laughter spread to over 1,000 people, leading to the closure of 14 schools. The epidemic lasted over a year. ### What was the recurrent mass hysteria in Nepal? Since the 1990s, a school in western Nepal has experienced recurrent outbreaks of mass hysteria, with students crying and writhing on the ground. These outbreaks occurred annually from 2016 to 2018 and were attributed to stress and anxiety. ### What are some theories about the cause of the Dancing Plague? Theories about the Dancing Plague include demonic possession, overheated blood, and ingestion of a fungus on mouldy bread acting like LSD. However, mass hysteria due to stress from poor living conditions is considered more likely. ### Why were nuns particularly susceptible to mass hysteria in the Middle Ages? Many convents were made up of young women forced into a life of celibacy and hard work, creating a breeding ground for psychological stress. Additionally, the religious and superstitious nature of the time contributed to bizarre group events. ### How was the Halifax Slasher incident resolved? The Halifax Slasher incident was resolved when one of the first victims admitted to self-inflicting their injuries. It was found that at least 9 of the 12 recorded victims had caused their injuries themselves, leading to the conclusion that there had never been a Slasher. ## Sources - [Original Side Projects video: 5 Strange Cases of Mass Hysteria](https://www.youtube.com/watch?v=BUA-ygKEodM) - [Hero image source](https://upload.wikimedia.org/wikipedia/commons/2/2f/UNICEF_Mitarbeiter_untersucht_Menschen_in_Aethiopien.jpg) by Nesbitt / openverse, by-sa. ## Related Coverage