Posted 09.24.2019 | by AMRA
The stress response is associated with brain activity in the amygdala and the prefrontal cortex. The amygdala initiates the fight, flight, or freeze response to fear-inducing stimuli, while the prefrontal cortex helps modulate this response. A higher degree of connectivity between these brain regions is thought to enhance emotional regulation. These conclusions are based on research with adults. Little is known about the neural basis for children’s responses to stress, however, and whether it can be beneficially modified by mindfulness-based interventions.
Bauer et al. [Behavioral Neuroscience] tested whether mindfulness training reduces stress levels in middle school children, and if so, whether it is done by inducing changes in the amygdala and its connectivity to a region of the prefrontal cortex. This is the first study investigating the effects of a mindfulness-based intervention on children’s brain activity.
All 6th graders in a Boston charter school were randomly assigned to an 8-week mindfulness training program or an 8-week computer coding training program. The researchers requested the 6th graders’ families to permit their children to participate in the functional magnetic imaging (fMRI) portion of the study. Forty children received permission (average age = 12 years; 70% female; 53% Caucasian; Average WASI IQ = 98), and 33 of their fMRI protocols were usable.
Mindfulness and computer coding groups met four times a week for 45 minutes during the last class of the school day. Each mindfulness session included 15 minutes of mindfulness exercises involving focused attention on the present moment and related didactic instruction and group discussion. Exercises included focused breath meditations, attention to the senses, open monitoring, and practice in noticing thoughts.
Control group sessions involved teaching the SCRATCH programming language using didactic instruction, collaborative learning, and group discussion. The SCRATCH program was developed by MIT Media Labs and is used around the world to introduce children to computer programming. All children completed self-report measures of perceived stress and positive and negative affect at baseline and post-intervention.
The children participating in the fMRI portion of the study were shown images of happy, fearful, and neutral facial expressions while undergoing scanning. They were scanned at baseline and post-intervention. Scans were analyzed for right amygdala reactivity to fearful facial expressions and amygdala functional connectivity with the ventromedial prefrontal cortex.
At baseline, stress level was associated with greater negative affect (r=.47) and less positive affect (r=-.37). As hypothesized by the researchers, baseline stress level (r=.41) and negative affect (r=.45) were significantly correlated with higher amygdala activation to fearful facial expressions.
At post-intervention, mindfulness participants had significantly greater reductions in stress levels (Cohen’s d=0.56) and a trend towards reduced negative affect (d=0.36) compared to controls. Right amygdala activation in response to fearful facial expressions decreased to a significantly greater degree (d=0.48) for mindfulness participants than controls. Stress change scores and amygdala activity change scores (r=.31) were significantly correlated in the mindfulness group only.
Functional connectivity between the amygdala and ventromedial prefrontal cortex while viewing fearful facial expressions significantly declined over time for the control group but not for the mindfulness group (Cohen’s f2=.27). At post-intervention, amygdala-prefrontal cortex functional connectivity was significantly greater for mindfulness participants than controls.
The study demonstrates the efficacy of a school-based mindfulness program in reducing middle-school children’s stress levels and amygdala activation to fear-related stimuli. This is the first mindfulness intervention study with children to use a brain-based marker to assess outcome. Mindfulness programs that reduce childhood stress may have an important role to play in reducing the incidence of mental health problems in adolescence and adulthood.
The study is limited by its requirement of obtaining parental permission for participants to undergo fMRI after randomization had already taken place.
Bauer, C. C. C., Caballero, C., Scherer, E., West, M. R., Mrazek, M. D., Phillips, D. T., . . . Gabrieli, J. D. E. (2019). Mindfulness training reduces stress and amygdala reactivity to fearful faces in middle-school children. Behavioral Neuroscience.