As the body of research into meditation grows, the evidence of the actual effect of meditating increases. Western science rarely provides clear evidence of causality, particularly when it comes to understanding complex human behavior such as meditation. However there are a significant number of studies that document a relationship between meditation and brain activity.
In 2012 a study was carried out into the effects of meditation (mindfulness and compassion methods) that had a direct effect on the response of a part of the brain called the amygdala to emotional stimuli. The headline findings from this study are that the changes to the amygdala response were measured while people were not meditating, meaning that the effects of an eight week meditation programme were experienced outside of meditation practise. Meditation had been able to exert an influence on people’s brains during a non-meditative state.
More details of this study at Science Daily.