Estrogen and Fear in PTSD

Prolonged-exposure (PE) therapy is the treatment of choice for posttraumatic stress disorder (PTSD). Despite its efficacy, a significant number of individuals will not benefit from it or might drop out before the completion of all sessions. This underlies the importance of findings ways to enhance the efficacy of PE in order to improve the life quality of individuals suffering from PTSD. It is now widely accepted that extinction learning paradigms used in fundamental studies are useful laboratory analogs to PE. Studies in healthy controls have suggested that elevated estrogen levels benefit extinction learning by promoting its consolidation and thus enhancing its recall when tested later for it. This is also being reflected by changes in the activation of brain regions forming the fear extinction network, including the amygdala, dorsal anterior cingulate cortex (dACC) and ventromedial prefrontal cortex (vmPFC). It is still unknown whether estradiol (E2) administration can modulate the activation of the fear extinction network in oral contraceptive (OC) users and which E2 dose could yield the best results. During the R61 phase of the study, we found that both doses of E2 were effective in engaging the functional activation of the fear extinction network. Therefore, we will use the lower dose (2mg) for the R33 phase. We will combine E2 administration with PE sessions to see if administration of PE can significantly improve clinical outcomes (reduced PTSD symptoms) and engage the fear extinction network in the brain. Hypothesis: A general improvement is expected after 3 weeks of treatment in both groups given the anticipated benefits of PE alone. But the benefit of the Estradiol-treated groups is hypothesized be larger; with this group exhibiting significantly higher activation in brain regions associated with fear extinction. This will be noted at the follow-up scan compared to the baseline scan. PTSD symptom severity expected be significantly lower in the Estradiol and PE group relative to the Placebo+PE group following acute treatment after three weeks of treatment. The degree of PTSD symptom reduction post- compared to pre-PE after 3 weeks of treatment is expected be associated with BOLD changes in the fear extinction network and reduction in SCR during the extinction recall test after PE. The magnitude of BOLD and SCR changes will be significantly larger in the E2+PE group compared to the Plc+PE group.