Meditation refers to any of a family of practices in which the practitioner trains his or her mind or self-induces a mode of consciousness in order to realize some benefit. Meditation is generally an internal, personal practice and most often done without any external involvement, except perhaps prayer beads to count prayers. Meditation often involves invoking or cultivating a feeling or internal state, such as compassion, or attending to a specific focal point. The term can refer to the state itself, as well as to practices or techniques employed to cultivate the state. There are dozens or more of specific styles of meditation practice. People may mean different things when they use the word, 'meditation'. Meditation has been practiced since antiquity as a component of numerous religious traditions, especially in monastic settings. A 2007 study by the U.S. government found that nearly 9.4% of U.S. adults (over 20 million) have practiced meditation within the past 12 months, up from 7.6% (more than 15 million people) in 2002. Since the 1960s, meditation has been the focus of increasing scientific research of uneven rigor and quality. In over 1000 published research studies, various methods of meditation have been linked to changes in metabolism, blood pressure, brain activation, and other bodily processes. Meditation has been used in clinical settings as a method of stress and pain reduction.