Mindfulness has been defined as "paying attention in a particular way: on purpose, in the present moment, and non-judgmentally." There has been a growing interest in mindfulness over the last few years and it has been shown to be effective in pain management, improving the function of the immune system, preventing relapses in depression, reducing anxiety and decreasing stress. However, less is known about how mindfulness works and under what circumstances. Researches at Fort Lewis College in Colorado studied 57 students. They were divided into four groups. One group did nothing (the control group), another group did a course of brief meditation focusing on breathing, sound and bodily sensations focusing on accepting whatever arises, a third group concentrated on extending compassion, friendliness, joy and peace to themselves and others and a fourth group did both meditation courses. The longer combined meditation group significantly reduced anxiety and negative affect and increased hope. The whole effect of the mindfulness intervention could be explained by its impact on cognitive distortions*, negative thoughts such as "it would be awful if...", "I couldn't cope with...," "People will think I'm a failure if..." etc.
Sears, Sharon and Kraus, Sue - I think therefore I om: cognitive distortions and coping style as mediators for the effects of mindfulness meditation on anxiety, positive and negative affect, and hope Journal of Clinical Psychology June 2009, 65(6), 561-573
*see http://en.wikipedia.org/wiki/Cognitive_distortions for an explanation of cognitive distortions