Summary

Worry and rumination are both forms of repetitive negative thought (RNT) characterized by repetitive and often uncontrollable thinking about negative content. Rumination is typically defined as repetitive thinking about the symptoms, causes, circumstances, meanings, and consequences of negative mood, personal concerns, and upsetting experiences, often with a focus on depressive experience. Worry is typically defined as repetitive thinking about future potential threat, imagined catastrophes, uncertainties, and risks and is conceptualized as an attempt to avoid negative events, prepare for the worst, and problem-solve. Worry and rumination are implicated in the exacerbation of negative mood and negative thinking, reduced central executive resources, impaired problem- solving, and prolonged sympathetic activation and emotional responses to stress and, as such, transdiagnostically contribute to the onset and maintenance of multiple emotional disorders, including major depression, anxiety disorders, insomnia, eating disorders, substance and alcohol abuse, and psychosis. Both worry and rumination are implicated in poor response to psychological interventions—greater reduction in RNT is associated with greater symptom improvement, whereas no change in RNT is associated with no improvement or worsening of symptoms. Rumination and worry appear to be moderately genetically heritable and predicted by environmental factors such as early adversity, stressful life events, and unhelpful parental styles. RNT is a common pathway between multiple risk factors, including neglect, abuse, bullying, and chronic stress, and later psychopathology. Pathological worry and rumination share an abstract processing style, negative biases in attention and interpretation, and impaired executive control and are mental habits. Both worry and rumination have been hypothesized to serve an avoidant function. Interventions that target these mechanisms appear to be effective at tackling RNT, particularly rumination-focused cognitive-behavioral therapy and mindfulness-based interventions. More efficient interventions for anxiety and depression may result from interventions that target multiple of these proximal mechanisms.