Federal health officials have offered some broad guidelines that communities should take, including identifying those at high risk, to head off possible "suicide clusters" among teenagers and young adults.

The national Centers for Disease Control said there is a growing public concern about recent suicide clusters among teenagers and young adults, but added, "Unfortunately our understanding of the causes and means of preventing suicide clusters is far from complete."The CDC said Thursday a statistical analysis of national mortality data indicates clusters of completed suicides occur predominantly among adolescents and young adults, and that such clusters account for between 1 and 5 percent of all suicides in this age group.

"Suicide clusters are thought by many to occur through a process of `contagion,' but this hypothesis has not yet been formally tested," CDC said. "Nevertheless a great deal of anecdotal evidence suggests that in any given suicide cluster suicides occurring later in the cluster often appear to have been influened by suicides occurring earlier in the cluster.

"Ecologic evidence also suggests that exposure of the general population to suicide through television may increase the risk of suicide for certain susceptible individuals, although the effect has not been found in all studies."

The CDC said it has helped several states and local health departments respond to clusters of attempted and actual suicides.

"Potential opportunities for prevention were often missed during the early stages of responses as community leaders searched for information on how best to respond to suicide clusters," the federal health agency said.

The CDC offered broad guidelines for dealing with suicide clusters, but said community leaders should review the guidelines and then develop their own response based on the needs of the particular community.

The guidelines the CDC suggested for meeting the threat of suicide clusters included:

-People who may be at high risk of suicide should be identified and have at least one screening interview with a trained counselor; they should be referred for further counseling or other services as needed.

-A timely flow of accurate, appropriate information should be provided to the media.

-Elements in the environment that might increase the likelihood of further suicides or suicide attempts should be identified and changed.