A Dynorphin Theory of Depression and Bipolar Disorder

TL;DR

This paper proposes a novel biological theory linking chronic dynorphin opioid signaling to the etiology, symptoms, and treatment of depression and bipolar disorder, emphasizing the role of stress response mechanisms.

Contribution

It introduces a new theory connecting dynorphin signaling to mood disorders, providing explanations for their mechanisms and treatment options.

Findings

Evidence for chronic dynorphin signaling in MDD

Dynorphin's causal role in depression demonstrated

Theory explains bipolar disorder mechanisms

Abstract

Major depressive disorder (MDD) is a debilitating health condition affecting a substantial part of the world's population. At present, there is no biological theory of MDD, and treatment is partial at best. Here I present a theory of MDD that explains its etiology, symptoms, pathophysiology, and treatment. MDD involves stressful life events that the person does not manage to resolve. In this situation animals normally execute a 'disengage' survival response. In MDD, this response is chronically executed, leading to depressed mood and the somatic MDD symptoms. To explain the biological mechanisms involved, I present a novel theory of opioids, where each opioid mediates one of the basic survival responses. The opioid mediating 'disengage' is dynorphin. The paper presents strong evidence for chronic dynorphin signaling in MDD and for its causal role in the disorder. The theory also explains bipolar disorder, and the mechanisms behind the treatment of both disorders.