The influence of work-related chronic stress on the regulation of emotion and on functional connectivity in the brain

Abstract

Despite mounting reports about the negative effects of chronic occupational stress on cognitive and emotional functions, the underlying mechanisms are unknown. Recent findings from structural MRI raise the question whether this condition could be associated with a functional uncoupling of the limbic networks and an impaired modulation of emotional stress. To address this, 40 subjects suffering from burnout symptoms attributed to chronic occupational stress and 70 controls were investigated using resting state functional MRI. The participants' ability to up- regulate, down-regulate, and maintain emotion was evaluated by recording their acoustic startle response while viewing neutral and negatively loaded images. Functional connectivity was calculated from amygdala seed regions, using explorative linear correlation analysis. Stressed subjects were less capable of down-regulating negative emotion, but had normal acoustic startle responses when asked to up-regulate or maintain emotion and when no regulation was required. The functional connectivity between the amygdala and the anterior cingulate cortex correlated with the ability to down-regulate negative emotion. This connectivity was significantly weaker in the burnout group, as was the amygdala connectivity with the dorsolateral prefrontal cortex and the motor cortex, whereas connectivity from the amygdala to the cerebellum and the insular cortex were stronger. In subjects suffering from chronic occupational stress, the functional couplings within the emotion- and stress-processing limbic networks seem to be altered, and associated with a reduced ability to down-regulate the response to emotional stress, providing a biological substrate for a further facilitation of the stress condition.

Figure 1. Overview of one experimental trial with the maintain instruction.

Participants were presented with a picture, which was replaced by an instruction cue. For negative picture trials, this cue indicated whether the participants' task was to maintain (horizontal arrow), down- regulate (downward arrow) or enhance (upward arrow) their emotional response. Immediately following the instruction cue, participants implemented the regulation instruction while being exposed to the same picture again. Lastly, participants rated how well they managed to implement the regulation instruction on a scale of 1–7.

Figure 2. Comparison between burnout patients and controls regarding startle reactions across task instructions.

The burnout group displayed overall higher responses when implementing instructions during negative pictures and this pattern was particularly pronounced during down- regulation of negative emotion. Note that the y-axis represents post-instruction response – pre- instruction response; * = p<.05.

Figure 3. Comparison between burnout patients and controls regarding rated regulation success across task instructions.

The burnout group rated themselves as generally less successful at implementing the task instruction after viewing negative pictures. * = p<.05, # = p<.1.

Figure 4. Group difference in resting state functional connectivity from the right amygdala (R amy).

Red clusters were calculated from the burnout group - control-group contrast (A), and blue clusters from the reverse contrast (B), (p<0.05 FWE corrected). Clusters are superimposed on the grey matter template (in the MNI space) from the entire study group. (C) Within group connectivity (positive) from the right amygdala. Blue clusters show connectivity clusters in controls, red clusters in the burnout group.

Figure 5. Yellow clusters denote significant interaction between the left amygdala connectivity map and the MBI-GS score merging both groups.

Pink clusters denote corresponding clusters from the right amygdala. Clusters calculated at p<0.05 FWE corrected, and superimposed on the grey matter template (in the MNI space) from the entire study group.