What Is Mass Hysteria?

Women in a group therapy session.
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What Is Mass Hysteria?

Also known as epidemic hysteria, mass psychogenic illness, and mass sociogenic illness, mass hysteria is a social phenomenon that involves groups of symptoms that imply some type of organic illness. However, these symptoms do not have an identifiable source and stem from psychological causes. They are shared by two or more people who also share a common belief about what might be causing the illness.

Despite the fact that mass hysteria originates in the mind, it can often produce real physiological symptoms and create severe psychological distress. Several factors can contribute to this phenomenon, including groupthink, stress, and social pressure.

Some psychologists believe mass hysteria is a form of groupthink. In cases of mass hysteria, the group members all develop a common fear that often spirals into a panic.

Signs of Mass Hysteria

This phenomenon affects groups of people, so many group members tend to exhibit these symptoms. Mass hysteria tends to be characterized by:

  • Symptoms that begin and end suddenly
  • An extensive investigation that reveals no clear medical explanation for these symptoms
  • Relatively benign symptoms such as dizziness, headaches, muscle twitches, headaches, or stomachache
  • Symptoms that appear to occur among specific social groups

People may begin exhibiting such symptoms after spending time together in a single location, which may lead people to suspect that the symptoms are due to a contagious illness or environmental contaminant. 

The problem is that mass hysteria is very difficult to identify as it is happening. In most cases, it is only apparent in retrospect after investigation and testing revealed no underlying illness or cause.

Causes of Mass Hysteria

While the exact causes of mass hysteria are not entirely understood, there are a number of different factors that might play a role. Some of these potential causes include:

Mass hysteria often begins with some type of environmental trigger. For example, a terrible smell followed by one or two people getting sick may lead the rest of the group to assume that the smell was an indicator of a poison or toxin. 


Groupthink is a psychological phenomenon that occurs when a group forms a quick opinion that matches the group consensus rather than critically evaluating the information. Groupthink is most often associated with business, politics, and policymaking, but it also relates to the psychology of collective phobias and mass hysteria. Mass hysteria can be seen as an extreme example of groupthink.

Groupthink seems to occur most often when a respected or persuasive leader is present, inspiring members to agree with their opinion. Groupthink is sometimes positive but is more often seen in a negative light, particularly in the U.S. and other countries that value individual opinion.


Experiencing extreme stress or trauma may also play a role in causing mass hysteria. When people are dealing with stressful or overwhelming situations, people may mistakenly attribute feelings related to stress as having a physical or environmental cause. So when people are subjected to collective trauma, they may begin to experience psychogenic symptoms.

Social Pressure

Social pressure may also play a part in feeling symptoms related to mass hysteria. When many people are exhibiting similar symptoms, people may either feel consciously or unconsciously pressured to also exhibit those same symptoms. Fearing that others are sick can cause people to pay too much attention to physical sensations, which may then be attributed to mass illness.

Some reports suggest that social media-induced illnesses, which are a form of mass hysteria, are becoming more common, particularly among teens.


It's believed that groupthink increases as group cohesiveness increases, which may help explain the psychological phenomenon of mass hysteria. Stress, social pressure, and environmental triggers also play a role.

Impact of Mass Hysteria

The group members feed off each other's emotional reactions, causing the panic to escalate. The Salem witch trials and the panic over the War of the Worlds radio broadcast can be viewed as examples of mass hysteria related to groupthink.

A widely publicized case of possible mass hysteria occurred in 2011 in upstate New York when teenage girls from the same high school began exhibiting an unexplained twitching disorder. They were later diagnosed with conversion disorder, although the diagnosis was met with opposition and anger among parents and the affected students.

An article published in American Ethnologist criticized the diagnosis as well. The article's authors suggested that the mass hysteria diagnosis served to dismiss the symptoms without adequately investigating environmental factors that may have played a role.

While mass hysteria is often a controversial diagnosis, the phenomenon is concerning because it can contribute to a number of other problems, including:

  • Public health issues
  • Missed work or school
  • Financial costs associated with missed work
  • Expenses connected to the attempted removal of non-existent environmental toxins

Mass hysteria can also create feelings of psychological distress. It can be extremely upsetting for people experiencing unexplained symptoms, particularly when no underlying causes can be found. However, it is also essential not to dismiss symptoms as a sign of mass psychogenic illness without seeking environmental or pathogenic origins adequately.

Some researchers have suggested that collective mass hysteria may have led to adverse consequences during the COVID-19 health pandemic, particularly as negative information spread through social networks and impacted public health and health-related behavior. 

How to Reduce Mass Hysteria

Mass hysteria is very difficult to detect as it is happening. In most cases, these incidences tend to be treated as serious potential public health issues. The source of the symptoms is investigated, and people may be treated for their unexplained symptoms.

There are a few different tactics that might help people avoid getting caught up in mass hysteria:

  • Separation: Being separated from people who are exhibiting unusual or unexplained symptoms might help reduce the impact on others.
  • Stress reduction techniques: Practice stress management strategies such as deep breathing, meditation, visualization, or progressive muscle relaxation might help people who are distressed by the unexplained symptoms that they or others are experiencing.
  • Psychotherapy: If mass hysteria appears to be affecting your health or behavior, talking to a therapist may be helpful. In addition to helping people cope, they can utilize therapeutic approaches such as cognitive behavioral therapy that help reduce negative or anxious thoughts that contribute to mass hysteria.

A Word From Verywell

Mass hysteria tends to be less common today than it was in the past, thanks to increased access to information. However, it still happens from time to time.

It is important to remember that it is most often noticed in retrospect. If people are experiencing symptoms that might be related to an illness or environmental toxin, it is important to take those experiences seriously and make sure that people get the diagnosis and appropriate treatment that they need.

Mass hysteria can have serious consequences. When many people are exhibiting similar behavior or experiencing similar symptoms, it is important to assess the situation and determine if there is an environmental cause. If mass hysteria is the culprit, finding ways to reduce the symptoms, such as relaxation and speaking to a therapist, may help.

Frequently Asked Questions

  • What causes mass hysteria?

    The exact causes are not fully understood, but groupthink, stress, social pressure, and environmental triggers appear to play a role.

  • Why is mass hysteria dangerous?

    Mass hysteria can lead people to seek medical treatments they don't need, create disruptions in people's lives, or lead to attempts to remove non-existent poisons or toxins. In some cases, it may lead people to seek out dubious treatments that might pose a danger to their health and well-being.

  • What are some examples of mass hysteria?

    While mass hysteria was more common in the past, there are cases of it occurring today. Following the 9/11 terrorist attacks, groups of elementary school children reportedly experienced skin rashes, but only while they were at school. The phenomenon was later described as a psychosomatic reaction to collective trauma. Social media may play a role in perpetuating mass hysteria today, although more research is needed to explore the phenomenon.

8 Sources
Verywell Mind uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  2. American Academy of Family Physicians. What is mass psychogenic illness? American Family Physician. 2000;15(62):2655-2656.

  3. Müller-Vahl KR, Pisarenko A, Jakubovski E, Fremer C. Stop that! It's not Tourette's but a new type of mass sociogenic illness. Brain. 2021 Aug 23:awab316. doi:10.1093/brain/awab316

  4. Szanto T. Collaborative irrationality, akrasia, and groupthink: Social disruptions of emotion regulationFront Psychol. 2017;7:2002. doi:10.3389/fpsyg.2016.02002

  5. Bartholomew RE, Wessely S, Rubin GJ. Mass psychogenic illness and the social network: is it changing the pattern of outbreaksJ R Soc Med. 2012;105(12):509-512. doi:10.1258/jrsm.2012.120053

  6. Goldstein DM, Hall K. Mass hysteria in Le Roy, New York: How brain experts materialized truth and outscienced environmental inquiry: How brain experts materialized truth. American Ethnologist. 2015;42(4):640-657. doi:10.1111/amet.12161

  7. Bagus P, Peña-Ramos JA, Sánchez-Bayón A. COVID-19 and the political economy of mass hysteriaInt J Environ Res Public Health. 2021;18(4):1376. doi:10.3390/ijerph18041376

  8. Talbot M. Hysteria, hysteria. The New York Times.

Additional Reading
  • Janis, I. Groupthink: The Desperate Drive for Consensus at Any Cost In: Shafritz, J. Ed. Classics of Organization Theory. Chapter 15, 2015.

  • Janis, I. Victims of groupthink: A psychological study of foreign-policy decisions and fiascoes. Houghton Mifflin. 1972.

By Lisa Fritscher
Lisa Fritscher is a freelance writer and editor with a deep interest in phobias and other mental health topics.