Prospective studies describing and predicting individual differences in the course of posttraumatic stress symptoms (PTSS) after disasters are scarce. The present study aimed to describe and predict individual differences in both the level and the rate of change in PTSS after the 2011 Oslo bombing, a terrorist attack directed at the Norwegian government. Survey data from ministerial employees (N = 256) were collected 10, 22, and 34 months after the bombing. We used latent growth modeling to examine the development of PTSS, and to identify the strength of predictor variables. High exposure, female sex, and high levels of neuroticism were associated with higher levels of PTSS 10 months after the traumatic event (β ranged from .25 to .30, p < .001), whereas social support was associated with lower levels of PTSS (β = -.30, p < .001). The combination of being female and high in neuroticism was associated with a faster decline in PTSS (β range: -.20 to -.39, p = .010 < .05). High exposure seemed to have a lasting influence by maintaining high levels of PTSS. Our findings suggested that being female, being highly exposed, and having low levels of social support were risk markers for enduring PTSS.
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