Context: Post-traumatic stress disorder (PTSD) is a chronic psychiatric disorder that occurs as a result of an accident or lifethreatening event. The purpose of our study was to examine the prevalence of PTSD in the Iranian population from 2000 to 2015 through a meta-analysis of the published studies to review the epidemiologic evidence of PTSD after disasters and wars and to examine PTSD determinants. Evidence Acquisition:The electronic databases including PubMed, Embase, Web of Science, Magiran, etc. were explored to find related papers. Two authors independently reviewed and extracted data via an extraction sheet, and disagreements were resolved by holding a meeting with a third author. Meta-analysis was performed using "metaprop" command in STATA 11 software. Studies with < 25 participants were excluded from our analysis. Results:Ultimately, 47 studies were included in this meta-analysis. Primary PTSD was investigated in 44 studies and secondary PTSD in six studies. Forty studies investigated natural PTSD and five studies technical PTSD. PTSD related to childbirth, job, earthquake, war, burn, accident, and rape events were investigated in seven, six, nine, nine, two, two, and two studies, respectively, and their pooled prevalence were 25%, 30%, 58%, 47%, 40%, 11%, and 74%, respectively. Conclusion:The results revealed that the burden of PTSD among the Iranian population exposed to wars and disasters is high. PTSD was correlated with a range of factors including demographic and background factors and characteristics of the event exposure.

Background: The study of the biological basis of fear in animal models has progressed considerably because of the energy and space that the brain devotes to this basic emotion. Electrical stimulation targets several structures of the brain to examine its behavioral effects and to understand the role of different regions in underlying mechanisms of fear processing and anxiety in preclinical models. Objectives: In this study, the effects of high-frequency deep brain stimulation (DBS) of the basolateral amygdala (BLA) and prelimbic (PL) sub-region of the prefrontal cortex were evaluated on the extinction process of conditioned fear. Methods: This study was performed on 35 male Wistar rats in the weight range of 220 – 250 g. After selecting the animals, they were separated into five groups. Then, we did stereotactic surgery on rats for electrode implantation. After recovery, some rats were conditioned, followed by a 10-day treatment schedule via high-frequency DBS in the BLA or PL. Next, freezing behavior was measured as a predicted response dedicated to extinction, without shock (re-exposure). In addition, we used ELISA and Western blot to estimate blood serum corticosterone levels and c-Fos protein expression. Results: The mean freezing time recorded for the PL group was significantly lower than that of both the BLA group and the PC group (P < 0.01). The BLA group and PC group were also significantly different (P < 0.001). Corticosterone results indicated that the PL group had significantly higher serum corticosterone levels compared with both the BLA group and the PC group (P < 0.01). In addition, the BLA group revealed a significant reduction in c-Fos expression compared with the PC (P < 0.001). Conclusions: This study provides further evidence for the contribution of the prelimbic cortex and amygdala both in acquisition and extinction processes during contextual fear conditioning. However, the PL stimulation by high-frequency DBS might be more involved in the extinction process and play a more important role as an enhancer.