Mindfulness-Based Stress Reduction (MBSR) is a manualized, systematic training in mindfulness meditation that has been found to have beneficial health effects, such as decreased stress and anxiety. The current protocol aims to examine the effects of MBSR on several physiological and behavioral measures in people with anxiety disorders, which may help us understand the effects of the intervention on anxiety. The investigators will use the NPU task as developed by the NIH, which measures an individual's response to threatening stimuli (mild shock) paired with non-threatening stimuli (geometric shapes). Individuals with anxiety disorders will be recruited to participate in this study, and will be randomized to a control (waitlist) or MBSR intervention group. Other secondary measures will examine the effects of mindfulness meditation on decision-making, and stress and anxiety symptoms.