Rumination predicts heightened responding to stressful life events in major depressive disorder and generalized anxiety disorder.

Although studies have documented heightened stress sensitivity in major depressive disorder (MDD) and generalized anxiety disorder (GAD), the mechanisms involved are poorly understood. One possible mechanism is the tendency to ruminate in response to stress. We used ecological momentary assessment to study ruminative thoughts after stressful events in 145 adults with MDD, GAD, comorbid MDD-GAD, or no psychopathology. Diagnosed individuals reported more event-related rumination than controls, even after adjusting for event stressfulness. Rumination was equally common in MDD and GAD and was especially severe among comorbid cases. More rumination immediately after the event predicted poorer affect, more maladaptive behavior, and more MDD and GAD symptoms at the next signal, even when pre-event levels of these variables were controlled. Rumination mediated, but did not moderate, the association of stress with affect and with symptoms. Stress-related rumination was more deleterious for diagnosed than healthy individuals, more intense for more severe clinical cases, and more persistent for cases with a greater temperamental vulnerability for emotional disorders. These results implicate rumination as a mechanism of stress sensitivity and suggest pathways through which it may maintain depression and anxiety in everyday life.