Several cognitive, behavioral, and emotional experiences are found across healthy and clinical populations and across distinct diagnostic categories. The present research was aimed at identifying processes (e.g., functional impairment, perfectionism, unwanted thought) that may operate across disorders to differentiate normal from abnormal experiences or increase risk for anxiety or mood symptoms. In Study 1, individuals diagnosed with generalized anxiety disorder (GAD), non-GAD high worriers, and normal worriers completed measures of perceived functioning and performance standards. Widespread functional impairments were reported both by individuals with GAD and by non-GAD high worriers. However, only non-GAD high worriers showed elevated performance standards, suggesting that different processes may account for the functional impairments perceived by these groups (i.e., recognition of diminished personal functioning versus inflated standards). Study 2 tested the association of appraisals of worried, ruminative, and obsessional thoughts to outcomes assessed concurrently and at 1-month follow-up. Across thought types, negative and positive appraisals were cross-sectionally associated with greater negative outcomes; positive appraisals were further associated with greater positive outcomes. Negative and positive appraisals of worry and rumination were also associated with increased negative outcomes at follow-up. These results suggest several similarities across thought types in the relationship between appraisals and outcomes, providing support for further transdiagnostic study of these processes. In Study 3, healthy participants were randomly assigned to receive negative, normalizing, or no feedback about their worried, ruminative, and obsessional thoughts to test the hypothesis that negative appraisals would lead to negative outcomes across thought types. Individuals' preexisting beliefs about thoughts were also expected to predict outcomes, both alone and in interaction with experimental condition. Unexpectedly, individuals in the Negative Feedback condition reported less negative outcomes than those in the other conditions, but these results were qualified by an interaction between preexisting beliefs and experimental condition across all thought types. These results suggest that preexisting negative beliefs about different forms of unwanted thought function as a cognitive vulnerability in interaction with specific stressors. Collectively, these studies suggest several features that may operate transdiagnostically to increase risk for symptom development or to differentiate normal from abnormal experiences of anxiety and depression.