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Why do two people who experience the same trauma react completely differently? Specifically; Who recovers spontaneously from trauma, and who develops lasting symptoms of posttraumatic stress? For most people, posttraumatic stress symptoms decline gradually during the first year after the traumatic exposure. Nonetheless, a significant number of people exposed to trauma develop posttraumatic stress symptoms that last for years and require support from clinical and public health professionals.

To better describe and understand individual differences in changes in posttraumatic stress over time, researchers at the Norwegian Centre for Violence and Traumatic Stress Studies (NKVTS) conducted a longitudinal study of posttraumatic stress in individuals who experienced a terrorist attack directed towards their workplace. The participants in the present study were employees in the Norwegian Ministries and present at work on 22 July 2011, when a right-wing terrorist triggered a bomb explosion in the centre of Oslo in the executive government quarter and the Ministries. Eight people were killed, at least 209 people were injured, and the office buildings were considerably damaged. (At the same day, another attack by the same terrorist took place at a youth camp at Utøya outside Oslo; 69 people were killed.)

We measured posttraumatic stress symptoms among the ministerial employees yearly the first three years after the event. As expected, we found that on average, the level of posttraumatic stress declined. Most of the change occurred during the two first years. People who were hurt themselves or witnessed others being hurt or killed, seem to experience longer-lasting symptoms of posttraumatic stress. The same was found for people lacking social support.

Women and people high in neuroticism, which involves a tendency to experience negative emotions, reported high initial levels but also a faster decline in posttraumatic stress symptoms than others. Even though their decline in symptoms was steeper, women continued to experience a higher level of symptoms of posttraumatic stress three years after the terrorist attack. In contrast, people high in neuroticism reported high initial levels of posttraumatic stress symptoms, and then declined to average three years after. Thus, high levels of neuroticism may not necessarily imply lasting high levels of posttraumatic stress. Neuroticism involves a tendency to arouse quickly when stimulated and to inhibit emotions slowly. This emotional lability may be important in explaining why neurotic people often respond stronger to stress. But as this study shows, this response may be transient. Interestingly, very low levels of neuroticism were associated with increasing levels of posttraumatic stress symptoms over time, and one may wonder whether these individuals initially suppressed symptoms or whether they developed them over time.

Many individuals experience a spontaneous recovery from the symptoms of posttraumatic stress during the first months or couple of years after the traumatic event, but after this, it seems like the level of posttraumatic stress stabilizes. An important implication of this is that people who have experienced traumatic events and that still experiences impairing symptoms after a year or two, should consult mental health support.
For clinicians it is important to acknowledge that individuals may be especially vulnerable to develop lasting high levels of posttraumatic stress if they have been severely exposed to traumatic events, are women, and/or lack social support.

Reference Article

Birkeland, M. S., Hansen, M., B., Blix, I., Solberg, Ø, & Heir, T. (in press). For Whom Does Time Heal Wounds? Individual Differences in Stability and Change in Posttraumatic Stress after the 2011 Oslo Bombing

Discussion Questions

1. Why does the recovery from posttraumatic stress symptoms seem to stagnate after a couple years?
2. Through which mechanisms do risk factors maintain high levels of posttraumatic stress symptoms?

About the Author

Marianne Skogbrott Birkeland, PhD, is a research psychologist at the Norwegian Centre for Violence and Traumatic Stress Studies.