Posted 07.21.2015 | by AMRA
Does mindfulness reduce stress by altering brain function? The amygdala—a small, almond-shaped structure located in the brain’s limbic system—is known to play a key role in the stress response. Previous research has shown that increased connectivity (a measure of the degree to which brain structures inter-coordinate) between the amygdala and other limbic and cortical structures is associated with greater stress levels.
In two separate studies, Taren et al. [Social Cognitive and Affective Neuroscience] investigated how the amygdala’s resting connectivity with nearby brain structures correlates with stress, and whether that connectivity changed in response to a mindfulness-based intervention (MBI). In doing so, the researchers aimed to identify one of the main brain pathways underlying the effect of mindfulness practice on stress levels. In an initial study, 130 healthy men and women self-reported perceived stress levels and participated in functional magnetic resonance imaging (fMRI) to assess the resting functional connectivity between the amygdala and nearby brain structures.
In a second randomized, single-blind study using an active control group, 35 unemployed adults with moderate-to-high levels of perceived stress were assigned to either a three-day intensive residential mindfulness retreat modeled after MBSR which included the body scan, sitting and walking meditation, and mindful eating and yoga, or a three day intensive relaxation retreat which included walking, stretching, and didactics emphasizing relaxation rather than mindfulness.
Amygdala connectivity was assessed by fMRI before and after each intervention. Four months later, hair samples were taken and assayed for stress hormone (cortisone and cortisol) levels over the post-intervention period. This study demonstrated that participants with higher levels of perceived stress had significantly greater degrees of connectivity between the right side of the amygdala and the subgenual anterior cingulate cortex (ACC) — a brain structure implicated in mood and affect disorders.
The randomized, controlled study showed that MBI participants, in comparison to controls, significantly decreased their amygdala-ACC connectivity. The greater the decrease in connectivity, the less cortisone and cortisol was found in hair samples four months later, strengthening the case for amygdala connectivity as a useful stress biomarker that can be modified through MBIs.
Taren, A. A., Gianaros, P. J., Greco, C. M., Lindsay, E. K., Fairgrieve, A., Brown, K. W., . . . Creswell, D.J,. (2015). Mindfulness meditation training alters stress-related amygdala resting state functional connectivity: A randomized controlled trial. Social Cognitive and Affective Neuroscience.