Suicide, Suicide Attempt, or Self-Harm Clusters

General Information About Clusters

In public health, a cluster is a greater-than-expected number of cases of a disease or occurrence that takes place among a group of people close in time, typically days or weeks. Criteria are usually developed to define a cluster. The group of cases are referred to as a suspected cluster until the parameters established by the criteria are met.

Common criteria include:

  • A greater-than-expected number: The observed number of cases is higher than typically observed in a similar setting.
  • A group of people: The population in which a cluster is occurring is carefully defined by factors such as age or sex for the purpose of calculating rates.
  • A connection between cases: The connection is typically a defined geographic area. The rates in this area may be compared with groups of people over a much larger geographic area, such as an entire state. The number of cases included in the cluster and calculation of the expected number of cases can depend on the definition of the geographic area where the cluster is occurring. Boundaries must be defined carefully. It is possible to “create” or “obscure” a cluster when selecting a specific area. People can also be connected in other ways, such as across social media platforms, occupation, or within specific institutions (such as schools or prisons).
  • A time period: The number of cases included in the cluster—and the expected number of cases calculation—will depend on the defined time period over which the cases occurred. Cases typically occur close in time.
General Information About Suicide-Related Clusters
  • A suicide cluster may be defined as a group of suicides, suicide attempts, or self-harm events that occur closer together in time and space than would normally be expected in a given community. The cluster may be one type of event or any combination of the three listed above. The space may be physically or virtually close.
  • The two most common types of suicide clusters are:
    • Point clusters (or spatial-temporal clusters): A greater-than-expected number of suicides that occur within a time period in a specific location. This might be in a community or an institution such as a school, university, or psychiatric inpatient setting.
    • Mass clusters (or temporal clusters): A greater-than-expected number of suicides within a time period that are spread out geographically.
  • Suicide and self-harm injuries often involve different injury methods. The most common suicide methods involve firearms, suffocation, and poisoning. The most common methods of self-harm are poisoning and cutting. However, the cluster cases do not necessarily need to involve the same injury method.
  • It may be difficult to determine if there are connections between cases or what the connection may be. For example, people in a cluster do not need to know each other. They may be connected by other factors such as having viewed the same social media content, connections to a third person who has died by suicide, or something else.
  • The connection between cases may be uncovered as a suspected cluster is under investigation.
  • Cases with obvious connections or those without apparent connections can both have similarly devastating consequences on friends, family, and communities.
  • A community response plan should consider identifying and referring persons who may be at high risk of suicide, regardless of whether the community-identified cluster involves a statistically significant greater-than-expected number of cases.
How to Report a Suicide-Related Cluster or Get Assistance

First, contact your local or state health department if you suspect a suicide-related cluster in your community, or if you’d like information such as suicide statistics or trends in your area. You can also find suicide data for your state or local area using CDC WISQARS or CDC WONDER. The local or state health department gathers information, develops a case definition, and determines whether there is a greater-than-expected number of cases. If the situation meets a cluster criteria, state and territorial public health authorities can request informal technical assistance, such as guidance or resources, or formal epidemiologic assistance from CDC through an Epi-Aid.

An Epi-Aid is an investigation of an urgent public health problem, such as infectious or non-communicable disease outbreaks, unexplained illnesses, or natural or manmade disasters. An Epi-Aid allows rapid, short-term (1–3 weeks), generally onsite, technical assistance by Epidemic Intelligence Service (EIS) officers and other CDC subject matter experts when a public health authority requests CDC’s assistance. The Epi-Aid investigation will assist partners in making rapid practical decisions for actions to prevent and control the public health problem.

Frequently Asked Questions
What is a suicide cluster?

Suicide clusters are defined as a greater-than-expected number of suicides or nonfatal events such as suicide attempts and self-harm occurring close in time or geography. Clusters can also imply relatedness on some other level than just statistical (for example, when vulnerable individuals from diverse locations are exposed to a highly publicized suicide and imitate the method of that suicide).


Niedzwiedz C, Haw C, Hawton K, Platt S. The Definition and Epidemiology of Clusters of Suicidal Behavior: A Systematic Review. Suicide Life Threat Behav; 2014; 44: 569-581.


Is there a way to statistically prove whether or not a cluster occurred?

It may be difficult to prove that a cluster occurred because of small numbers. There are statistical methods available that can be applied, such as geographic information systems, Knox, Poisson, or Scan tests.



What does suicide contagion mean?

Suicide contagion is the process by which suicide or suicidal behavior influences an increase in the suicidal behaviors of others.


  • O’Carroll P. Suicide prevention: Clusters and contagion. In: Berman AL, editor. Suicide Prevention: Case Consultations. New York: Springer, 1990.
  • Cheng Q, Li H, Silenzio V, Caine ED. Suicide contagion: A systematic review of definitions and research utility. PLoS One. 2014; 9(9): e108724. doi: 10.1371/journal.pone.0108724.


Does media attention (such as social media, news reports, and entertainment media) affect suicidal behavior?

Risk of suicide can increase when media reports fail to follow best practices, including:

  • Dramatic or graphic headlines or images
  • Repeatedly reporting on the same suicide
  • Explicitly describing the suicide method or showing pictures of it
  • Dramatizing the suicide death through romanticized or sensational headlines
  • Showing the site of the suicide and pictures of those who are grieving

Media can play an important role in preventing suicide risk or deaths by following Best Practices and Recommendations for Reporting on Suicide. For example, media can:

  • Provide information on warning signs of suicide risk
  • Provide resources for how to get help, including local or national hotlines
  • Share messages of hope and resilience
  • Engage experts to provide facts about suicide and how to prevent it



Where are suicide clusters more likely to occur?

There is no one place where clusters are more likely to occur. Published investigations of suicide clusters have shown that they occur in a variety of locations and settings such as schools, correctional facilities, military institutions, and hospitals.



What are the risk factors associated with suicide clusters?

Risk factors for individuals involved in suicide clusters include male sex, being an adolescent or young adult, excessive alcohol use, drug misuse, and past history of self-harm.


Haw C, Hawton K, Niedzwiedz C, Platt S. Suicide clusters: A review of risk factors and mechanisms [PDF – 12 pages]. Suicide Life Threat Behav. 2013; 43(1): 97-108.


What age group has more clusters?

Among published reports, adolescents and young adults seem to experience clusters more frequently than middle-aged or older adults. In the United States, approximately 1% to 5% of teen suicides occur as part of a cluster.



How can a community respond when a suicide cluster occurs?

CDC recommends three general phases of action to prevent and respond to clusters: preparedness, intervention/postvention, and follow-up. These phases are briefly discussed below.


  • A community should review recommendations and develop a response before the onset of a suicide cluster.
  • A crisis plan and response should involve all concerned sectors of the community and should be coordinated by:
    • a coordinating committee which manages the day-to-day crisis response, and
    • a host agency whose responsibilities would include “housing” the plan, monitoring the incidence of suicide, and calling meetings of the coordinating committee when necessary.
  • The relevant community resources should be identified.


  • The response plan should be implemented under either of the following two conditions:
    • when a suicide cluster occurs in the community, or
    • when one or more deaths from trauma occur in the community, especially among adolescents or young adults, which may potentially influence others to attempt or complete suicide.
  • The first step of a response plan should be to contact and prepare those groups who will play key roles in the first days of the response.
  • The response should avoid glorification of the suicide victims and minimize sensationalism.
  • People who may be at high risk of suicide should be identified and have at least one screening interview with a trained counselor. These people should be referred for further counseling or other services as needed.
  • The media should have a timely flow of accurate, appropriate information.

Follow up

  • Elements in the environment that might increase the likelihood of further suicides or suicide attempts should be identified and changed.
  • Long-term issues suggested by the nature of the suicide should be addressed.


Need help? Know someone who does?

Contact the 988 Suicide and Crisis Lifeline if you are experiencing mental health-related distress or are worried about a loved one who may need crisis support.

Connect with a trained crisis counselor. 988 is confidential, free, and available 24/7/365.

Visit the 988 Suicide and Crisis Lifeline for more information at