Psychobiology of the intersection and divergence of depression and anxiety

Mounting evidence highlights substantial genetic, neurobiological, and symptomatic overlap between depression and anxiety disorders, suggesting that current classification systems do not “carve nature at its joints.” Stemming from this is a notable lack of precision in treatment selection, and frontline treatments for depression and anxiety disorders fail to relieve symptoms in many patients. For example, up to 50% of individuals with major depression failed to respond to antidepressant treatments, and only one in three patients achieved remission (full recovery) within the nationally representative Sequenced Treatment Alternatives to Relieve Depression (STAR*D) study (Trivedi et al., 2006). Response rates for psychotherapy (e.g., cognitive or behavioral therapies) show similar patterns, with about 50% of individuals with major depression (Cuijpers et al., 2014) or anxiety (Loerinc et al., 2015) displaying a beneficial response. As outlined in a series of recent reviews (e.g., Hyman, 2010; Insel et al., 2010; Pizzagalli, 2014), there are several reasons for the modest success in treating these prevalent and debilitating disorders. These include a high degree of comorbidity (reaching to up 75% in clinical samples [e.g., Sørensen, Nissen, Mors, & Thomsen, 2005]), the considerable heterogeneity of diagnostic syndromes as conceptualized by current classification systems (e.g., Diagnostic Statistical Manual, International Classification of Diseases), and an incomplete understanding of the pathophysiology and etiology of depression and anxiety disorders. Together, these constitute a formidable barrier to treatment development and implementation. To address these challenges and also highlight exciting new developments, the Scientific Research Symposium held during the 2015 Annual Meeting of the Anxiety and Depression Association of America (ADAA) was centered on the psychobiology of the intersection and divergence of depression and anxiety. The goal of this symposium was to feature and integrate recent advances in our understanding of the pathophysiology, manifestation, course, and treatment of depression and anxiety disorders. In particular, through a “bench to bedside approach” that emphasized cross-species convergence, integration of different levels of analysis (e.g., molecules, brain circuitry, behavior, self-report), consideration of developmental trajectories, and a focus on well-characterized phenotypes that cut across diagnostic boundaries (e.g., reward and threat sensitivity, fear extinction), this symposium aimed to highlight major advances that are illuminating shared and unique features of depression and anxiety and identifying novel targets for treatments. All symposium speakers submitted review or empirical papers for the current special issue. In this editorial, I provide a brief synopsis of each contribution, highlight areas of intersection and synergies, and underscore unanswered questions that should be addressed in future research. 1 KAPPA OPIOID ANTAGONISTS AND STRESS-INDUCED NEUROADAPTATION