Transmission is an important concept in suicide prevention. It can occur when exposure to another person's death by suicide (or to suicide-related information more generally) draws attention to suicide or highlights specific suicide methods.

In this paper, the fourth in a series on a public health approach to suicide prevention, we contend that the transmissibility of suicide must be considered when determining optimal ways to address it. We draw on five examples of how transmission might occur and be prevented.

The first two examples relate to transmission initiated by representations of suicide in traditional and new media. The third concerns transmission that leads to suicide clusters, and the fourth considers a specific setting in which transmission occurs, namely secondary schools.

Finally, we discuss how suicide risk might be countered by the transmission of suicide prevention messages in media campaigns.