Suicide is one of the major causes of death in young people, in whom suicide can occur
in clusters. In this Review, we have investigated definitions and epidemiology of
such clusters, the factors associated with them, mechanisms by which they occur, and
means of intervening and preventing them. Clustering of suicidal behaviour is more
common in young people (<25 years) than adults. Suicide clusters can occur as a greater
number of episodes than expected at a specific location, including in institutions
(eg, schools, universities, psychiatric units, and youth offender units). They might
also involve linked episodes spread out geographically. Locations exposed to clusters
can be at risk for future clusters. Mechanisms involved in clusters include social
transmission (particularly via person-to-person transmission and the media), perception
that suicidal behaviour is widespread, susceptible young people being likely to socialise
with others at risk of suicidal behaviour, and social cohesion contributing to the
diffusion of ideas and attitudes. The internet and social media might have particularly
important roles in spreading suicidal behaviour. The effect of suicide clusters on
communities and institutions is usually profound. Experience of intervening in clusters
has resulted in best practice guidance. This guidance includes preparation for occurrence
of clusters in both community and institutional settings. Identification of clusters
in the community requires real-time monitoring of suicidal behaviour. Effective intervention
is more likely if a cluster response group is established than if no such group exists.
The response should include bereavement support, provision of help for susceptible
individuals, proactive engagement with media interest, and population-based approaches
to support and prevention. Social media can provide a powerful means for disseminating
information and reaching young people at risk.