Long-term meditators had 9081 hours of lifetime practice on average, primarily in mindfulness meditation. Short-term training consisted of an eight-week mindfulness-based stress reduction (MBSR) course. The control group, made up of people with no meditation experience, was randomly assigned to a ‘health enhancement program’ over the same time period that included well-being practices, but not meditation specifically.
Study: Krak T R A et al. ‘Impact of short- and long-term mindfulness meditation training on amygdala reactivity to emotional stimuli.’ NeuroImage vol 181, 1 November 2018, 301-313.