Lower estradiol predicts increased reinstatement of fear in women

An investigation of the role of estradiol in fear reduction during a single session of exposure therapy

Research suggests that estradiol may moderate fear extinction. It is unclear whether these results generalize to exposure therapy. The aim of the current study was to determine whether estradiol moderates outcomes in exposure therapy among women with anxiety disorders. Participants were 35 women with a primary diagnosis of an anxiety disorder who participated in the study as part of routine care at an anxiety specialty clinic. Endogenous estradiol was assessed via saliva. They provided subjective distress ratings before (pre) and after (post) an exposure session, as well as after a brief delay (recall). Contrary to predictions, there were no significant differences in exposure outcomes between the high and low estradiol groups. However, among participants with primary obsessive-compulsive disorder (OCD), results were partially consistent with the hypotheses. Women with lower estradiol initially demonstrated more improvement in subjective distress from pre- to post-exposure, but after the delay, significantly greater distress (attenuated extinction recall). Results suggest that women with lower estradiol may respond less favorably to exposure therapy for OCD relative to women with higher estradiol. These findings await replication in larger samples with longer recall delays. Should replication occur, these results may inform the use of estradiol to augment exposure therapy.

The neurobiology of Pavlovian safety learning: Towards an acquisition-expression framework

Safety learning creates associations between conditional stimuli and the absence of threat. Studies of human fear conditioning have accumulated evidence for the neural signatures of safety over various paradigms, aligning on several common brain systems. While these systems are often interpreted as underlying safety learning in a generic sense, they may instead reflect the expression of learned safety, pertaining to processes of fear inhibition, positive affect, and memory. Animal models strongly suggest these can be separable from neural circuits implicated in the conditioning process itself (or safety acquisition). While acquisition-expression distinctions are ubiquitous in behavioural science, this lens has not been applied to safety learning, which remains a novel area in the field. In this mini-review, we overview findings from prevalent safety paradigms in humans, and synthesise these with insights from animal models to propose that the neurobiology of safety learning be conceptualised along an acquisition-expression model, with the aim of stimulating richer brain-based characterisations of this important process.

Using Translational Models of Fear Conditioning to Uncover Sex-Linked Factors Related to PTSD Risk

Post-traumatic stress disorder (PTSD) is a debilitating neuropsychiatric disorder that follows exposure to a traumatic event; however, not every person who experiences trauma will develop PTSD. Women are more likely to be diagnosed with PTSD than men even when controlling for type and amount of trauma exposure. Circulating levels of gonadal hormones such as estradiol, progesterone, and testosterone may contribute to differential risk for developing PTSD. In this review, we briefly consider the influence of gonadal hormones on fear conditioning processes including fear acquisition, fear inhibition, extinction learning, and extinction recall within translational neuroscience models. We discuss findings from human studies incorporating samples from both community and traumatized clinical populations to further understand how these hormones might interact with exposure to trauma. Additionally, we propose that special attention should be paid to the specific measure used to examine fear conditioning processes as there is evidence that common psychophysiological indices such as skin conductance response and fear-potentiated startle can reveal quite different results and thus necessitate nuanced interpretations. Continued research to understand the influence of gonadal hormones in fear learning and extinction processes will provide further insight into the increased risk women have of developing PTSD and provide new targets for the treatment and prevention of this disorder.

Translation of animal endocannabinoid models of PTSD mechanisms to humans: Where to next?

The endocannabinoid system is known to be involved in mechanisms relevant to PTSD aetiology and maintenance, though this understanding is mostly based on animal models of the disorder. Here we review how human paradigms can successfully translate animal findings to human subjects, with the view that substantially increased insight into the effect of endocannabinoid signalling on stress responding, emotional and intrusive memories, and fear extinction can be gained using modern paradigms and methods for assessing the state of the endocannabinoid system in PTSD.