MBSR is, as described in a 2003 meta-review of current scientific literature on Mindfulness-based stress reduction, "MBSR is a group program that focuses upon the progressive acquisition of mindful awareness, of mindfulness. The construct of mindful awareness originated in earliest Buddhist documents but is neither religious nor esoteric in nature. Several Buddhist treatises detail an elaborate psychological theory of mind, in which mindfulness consistently plays a central role. Mindfulness is characterized by dispassionate, nonevaluative and sustained moment-to-moment awareness of perceptible mental states and processes. This includes continuous, immediate awareness of physical sensations, perceptions, affective states, thoughts, and imagery. Mindfulness is nondeliberative: It merely implies sustained paying attention to ongoing mental content without thinking about, comparing or in other ways evaluating the ongoing mental phenomena that arise during periods of practice. Thus, mindfulness may be seen as a form of naturalistic observation, or participant-observation, in which the objects of observation are the perceptible mental phenomena that normally arise during waking consciousness."