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Describe your research and the big picture problem or puzzle it addresses.

While many 9/11 World Trade Center First responders developed posttraumatic stress disorder, or PTSD, the way that the symptoms presented differs across individuals. For example, some first responders had many of the classic symptoms of PTSD (e.g., hyperarousal, nightmares, depressed mood, and avoidance), while others had more specific combinations of symptoms.

What did you do?

We used a statistical approach called latent class analysis (LCA), which helps identify how symptoms may cluster together to form different “classes” of a disorder. Since PTSD is very heterogeneous (e.g., there are many possible symptoms and the disorder can look vastly different in two people), this approach helps us understand how and why certain types of symptoms cluster together. We used this approach on 4352 World Trade Center responders who had PTSD.

What did you find?

We found that there were three “classes” of PTSD in first responders– e.g., there were three distinct patterns of PTSD. One class was High-Symptom, where the first responder experienced almost all symptoms of PTSD. Another class was predominantly “Dysphoric” symptoms, like emotional numbing and sleep disturbances. A third class, labeled “Threat”, had more re-experiencing symptoms, like nightmares and anxious arousal. The three classes were related to different experiences and outcomes. The High-Symptom class was more likely than the Dysphoric class, which was more likely than the Threat class, to have depression (83% > 74% > 53%, respectively), and to report greater functional impairment.

Describe the limitations.

This study was cross-sectional, so were unable to study how these classes of PTSD evolved over time. We also cannot make conclusions on causality and can only comment on how these classes correlate with predictors and outcomes.

What are the takeaways?

PTSD is a heterogeneous disorder and it is useful to understand how people exposed to traumatic exposures may develop and present with certain types of symptoms. This information can guide treatment planning and intervention approaches.

Horn, S. R., Pietrzak, R. H., Schechter, C., Bromet, E. J., Katz, C. L., Reissman, D. B., … & Luft, B. J. (2016). Latent typologies of posttraumatic stress disorder in World Trade Center responders. Journal of psychiatric research83, 151-159.



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