Imbalance of approach and avoidance: the yin and yang of anxiety disorders.

wo interesting articles from Harvard University investigators in this issue of Biological Psychiatry challenge us to reconsider and rethink the complexities of the underlying eurobiology of posttraumatic stress disorder (PTSD). We refer o these articles with a view to highlighting their unique contriutions to the literature and the new directions they motivate for ranslational research in PTSD and other anxiety disorders. Milad and colleagues (1) used an operant conditioning paraigm to show that patients with PTSD have deficient extinction etention relative to trauma-exposed control subjects who had ot developed PTSD. They further demonstrate, using functional RI (fMRI), that this reduced extinction retention is related to ess activation in the hippocampus and bilateral ventromedial refrontal cortex in patients with PTSD. This article underscores ur growing appreciation that PTSD is characterized by dysfuncion of “unlearning” within fear circuitry, and the findings should otivate clinical research to enhance extinction retention hrough pharmacologic and other means. Such approaches, in arallel with those aimed at the disruption of the consolidation of ear memories, are among the most promising translational leads or PTSD therapeutics (2). In contrast to the aforementioned study, which adds imporant information to the burgeoning literature on abnormal fear ircuitry and deficient fear extinction mechanisms in PTSD, the rticle by Elman and colleagues (3) delves into a much neglected rea: the study of reward processing in PTSD. Consistent with a revious report of altered processing in the reward circuitry of atients with PTSD (4), these investigators found less striatal ctivation to monetary gains versus losses in PTSD in association ith more self-reported motivational and social deficit. These bservations can be considered complementary to those that find lterations in fear-motivated systems that underlie behavioral voidance in PTSD (and, possibly, other anxiety disorders) in hat they point to dysfunction in brain systems that underlie eficient approach behaviors. Reward circuitry has been largely eglected in the study of PTSD, and this article (3) should be onsidered a call to action to intensify research on this topic. hat can be gained by integrating investigation of reward ystems in PTSD? It has long been recognized that individuals balance the pproach system, which is closely related to reward processes ith the avoidance system, which focuses on fear-related proesses (5). Nearly all research to date on PTSD has been focused n fear, therefore ignoring the “yin-yang” of approach–avoidnce that underlies all anxiety disorders, including PTSD. We uggest that PTSD is a disorder characterized by imbalance of pproach–avoidance systems. By considering both aspects when onceptualizing the dysfunctions observed in individuals with