Serum cortisol and neuroticism for post‐traumatic stress disorder over 2 years in patients with physical injuries.

Aim: This study aimed to explore the relationships between serum cortisol levels, personality traits, and the development of Post‐Traumatic Stress Disorder (PTSD) over 2 years among individuals with physical injuries. Methods: Participants were consecutively recruited from a trauma center and followed prospectively for 2 years. At baseline, serum cortisol levels were measured, and personality traits were categorized into five dimensions (Extraversion, Agreeableness, Conscientiousness, Neuroticism, and Openness), using the Big Five Inventory‐10. The diagnosis of PTSD during follow‐up (at 3, 6, 12, and 24 months post‐injury) was determined using the Clinician‐Administered PTSD Scale for DSM‐5. Binary and multinomial logistic regression analyses were conducted to examine the interactions between cortisol levels, personality traits, and PTSD development. Results: Among 923 patients analyzed, 112 (12.1%) were diagnosed with PTSD at some point during the study period, with prevalence rates decreasing from 8.8% at 3 months to 3.7% at 24 months post‐injury. Direct associations between cortisol levels or personality traits and PTSD were not observed. However, a significant interaction between lower cortisol levels and higher Neuroticism in relation to PTSD risk was identified, especially during the early follow‐up periods (3 to 6 months), but this association waned from the 12‐month follow‐up onward. Conclusion: Our findings reveal Neuroticism‐dependent associations between serum cortisol levels and PTSD development, exhibiting temporal variations. These results suggest that PTSD development may be influenced by a complex, time‐sensitive interplay of biological and psychosocial factors, underscoring the importance of considering individual differences in stress reactivity and personality in PTSD research and treatment. [ABSTRACT FROM AUTHOR]