Mindfulness is the practice of purposely bringing one's attention to the present-moment experience without evaluation, a skill one develops through meditation or other training. Mindfulness derives from sati, a significant element of Hindu and Buddhist traditions, and is based on Zen, Vipassanā, and Tibetan meditation techniques. Though definitions and techniques of mindfulness are wide-ranging, Buddhist traditions explain what constitutes mindfulness such as how past, present and future moments arise and cease as momentary sense impressions and mental phenomena. Individuals who have contributed to the popularity of mindfulness in the modern Western context include Thích Nhất Hạnh, Herbert Benson, Jon Kabat-Zinn, Richard J. Davidson, and Sam Harris.

Clinical psychology and psychiatry since the 1970s have developed a number of therapeutic applications based on mindfulness for helping people experiencing a variety of psychological conditions. Mindfulness practice has been employed to reduce depression, stress, anxiety, and in the treatment of drug addiction. Programs based on mindfulness models have been adopted within schools, prisons, hospitals, veterans' centers, and other environments, and mindfulness programs have been applied for additional outcomes such as for healthy aging, weight management, athletic performance, helping children with special needs, and as an intervention during the perinatal period.

Clinical studies have documented both physical- and mental-health benefits of mindfulness in different patient categories as well as in healthy adults and children. Studies have shown a positive relationship between trait mindfulness (which can be cultivated through the practice of mindfulness-based interventions) and psychological health. The practice of mindfulness appears to provide therapeutic benefits to people with psychiatric disorders, including moderate benefits to those with psychosis. Studies also indicate that rumination and worry contribute to a variety of mental disorders, and that mindfulness-based interventions can enhance trait mindfulness and reduce both rumination and worry. Further, the practice of mindfulness may be a preventive strategy to halt the development of mental-health problems. However, according to one opinion article, too much mindfulness may produce negative effects.

Evidence suggests that engaging in mindfulness meditation may influence physical health. For example, the psychological habit of repeatedly dwelling on stressful thoughts appears to intensify the physiological effects of the stressor (as a result of the continual activation of the sympathetic nervous system and the hypothalamus-pituitary-adrenal axis) with the potential to lead to physical health related clinical manifestations. Studies indicate that mindfulness meditation, which brings about reductions in rumination, may alter these biological clinical pathways. Further, research indicates that mindfulness may favorably influence the immune system as well as inflammation, which can consequently impact physical health, especially considering that inflammation has been linked to the development of several chronic health conditions. Other studies support these findings. Additionally, mindfulness appears to bring about lowered activity of the default mode network of the brain, and thereby contribute towards a lowered risk of developing conditions such as dementia and Alzheimer's disease.

However, critics have questioned both the commercialization and the over-marketing of mindfulness for health benefits—as well as emphasizing the need for more randomized controlled studies, for more methodological details in reported studies and for the use of larger sample-sizes. While mindfulness-based interventions may be effective for youth, research still needs to determine the most appropriate methods in which mindfulness could be introduced and delivered in schools.