Major depression is one of the most prevalent and debilitating personal and public health conditions worldwide. Less appreciated is that depression's tremendous burdens are not shared equally among all who become depressed. Some will suffer recurrences over the rest of their lives, whereas half or more will never have a recurrence. Based on these two distinctive life course prototypes, we propose a subtype distinction for research on the origins and lifetime course of major depression. A pressing goal is to determine at the time of depression's first onset who will follow which clinical trajectory. The lack of recognition of this distinction has resulted in many obstacles, including conceptual biases, methodological oversights, and definitional dead ends. Current theories are reviewed and compared. The implications for contemporary diagnostic controversies, reevaluating research on treatment and prevention, and enhancing the predictive strength of traditionally weak indicators of recurrences and recurrent depression are discussed.
Keywords: dual pathway models; life stress; major depression; recurrence; recurrent depression; stress sensitization.