The University of Western Sydney study also revealed that survivors were emotionally better off if they were married with family support or were in a relationship.
Though the survivors were in good physical health, they did suffer increased emotional trauma.
Lead author Garry Stevens said, "Deaths involving deliberate violence are associated with higher incidence of depression and prolonged or 'complicated' grief and a slower rate of recovery."
"Half of the group interviewed reported that, in the previous month, they had experienced upsetting thoughts, dreams or're-experiences' related to the Bali bombing or the need to avoid such thoughts and feelings," Co-author and a senior NSW Ministry of Health psychologist Julie Dunsmore said.
All post-disaster screening programs should evaluate people for long-term psychological impact, and treatment options should be made available for a longer period of time.