Killing two birds with one stone: how intervening when witnessing bullying at the workplace may help both target and the acting observer.

Objective: This study examines under which conditions being an observer of bullying can be detrimental to health and well-being. It was hypothesized that health-related problems following observations of bullying are determined by (1) whether the observer has been exposed to bullying her/himself and (2) whether the observer have tried to intervene in the bullying situation that they witnessed.
Methods: The study was based on a longitudinal probability survey of the Swedish workforce, with an 18-month time lag between assessment points (N = 1096).
Results: Witnessing bullying at work were associated with an increase in subsequent levels of mental distress among the observers, although this association became insignificant when adjusting for the observers' own exposure to bullying. Intervening against bullying moderated the relationship between observations of bullying and mental health problems. Observers who did not try to intervene reported a significant increase in mental health problems at follow-up, whereas there were no significant changes in levels of mental health problems among those who did intervene.
Conclusions: the findings suggest that observer interventions against bullying may be highly beneficial for both the targets and observers of bullying. Organizations should therefore invest in ways to increase constructive bystander behavior in negative social situations at the workplace.