Post-traumatic stress disorder (PTSD) is an anxiety disorder that may develop after the experiencing or witnessing of a life-threatening event. PTSD is defined by the coexistence of three clusters of symptoms: re-experiencing, avoidance and hyperarousal, which persist for at least 1 month in survivors of the event (Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition). Using an established model of PTSD, we addressed the well-accepted clinical finding that only a minority (about 20%) of the individuals exposed to a traumatic event develop PTSD. Moreover, we followed individual rat behavior for up to a month, and then treated the PTSD-like animals with citalopram. Our data demonstrate high face (20% of rats exposed to a reminder of the stressor develop symptoms characteristic of PTSD) and predictive (response to citalopram) validities. Based on these validities we identified alterations in the Wolframin gene in the CA1 and amygdala regions, specifically in exposed PTSD-like rats, which were normalized after treatment with citalopram. We suggest the Wolframin gene as a putative biomarker for PTSD. Since Wolframin gene undergoes alternative splicing and has polymorphism in the population, it may serve a future marker for identification of the vulnerable population exposed to a traumatic event.