Long-term relationships between perceived social support and posttraumatic stress after the 2011 Oslo bombing: A three-year longitudinal study.

Background: After traumatic events, social support and posttraumatic stress are interrelated, but little is known about the underlying dynamics behind this association. Levels of social support and posttraumatic stress may change and affect each other over time, but there are also stable time-invariant individual differences in both constructs. The present study aimed to determine the amount of variance explained by stable individual differences in levels of social support and posttraumatic stress across three years, and to determine whether and to what extent social support and posttraumatic stress may affect one another when these stable individual differences are controlled for.

Methods: We used data from ministerial employees present in the Governmental district during the 2011 Oslo bombing attack (N=255). Data was collected ten months, two years, and three years after the terror attack. Using a random intercept cross lagged panel model (RI-CLPM), we tested the possible directional effects between social support and posttraumatic stress within persons when variance between persons was taken into account.

Results: The intraclass correlations of the three measures of posttraumatic stress and social support were.83 and.74, respectively. The remaining variation within persons could not be explained by change in either of these constructs.

Limitation: We have no information on the processes that might have occurred before 10 months after the incident.

Conclusions: Our findings indicate that the long-term longitudinal linkage between social support and posttraumatic stress may be best explained by stable individual differences rather than causal processes operating within persons.