In this paper, we want to examine the effect of increased levels of anxiety on the brain and body in order to understand its adverse consequences for mental and physical functioning and well-being. Previous research indicated that anxiety causes a left-hemispheric bias of the brain, decreases amygdala activity, increases hippocampal-insula activity, and elevates blood pressure. In our first (correlational) study, we tested the strength of these relationships by examining naturalistic daily changes in their variables longitudinally over a two-week period. We rated the level of anxiety on a scale of 0 to 100, measured left-hemispheric bias by the Global Local task, determined amygdala activity by increases in heart rate after watching scary videos, measured hippocampal-insula activity by the number of memory-induced gut feelings experienced each day, and measured blood pressure by diastolic readings. Data pooled across participants in our correlational study showed a significant correlation of anxiety level with hippocampal-insula activity and blood pressure in half of the participants but not with amygdala activity and hemispheric bias. Based on the strength of correlation found between anxiety level and hippocampal-insula activity in our correlational study, we then conducted a second (experimental) study to test for specifically a causal relationship between these two variables. Over a twelve-day period, we randomly assigned participants each day to either a guided meditation condition or a social media condition and measured the effect this had upon anxiety level each day. The results of our experimental study failed to establish a causal role of anxiety level upon hippocampal-insula activity in most of the participants, with only one participant showing a significant effect. A possible practical application of these findings could be that increased memory-induced gut feelings might indicate higher than usual anxiety in some people.
