The effects of acute inflammation on cognitive functioning and emotional processing in humans: A systematic review of experimental studies

- This review investigates the effects of experimental inflammation on cognitive processing in humans.
- We found strongest evidence for experimental inflammation on negative biases in emotional processing.
- The effects of experimental inflammation on attention/executive functioning and memory were mixed.
- These observed effects on social/emotional processing might explain how inflammation causes depression.
- Further research into emotional processing among people with inflammatory states is required.

ObjectiveThe cognitive neuropsychological model of depression proposes that negative biases in the processing of emotionally salient information have a central role in the development and maintenance of depression. We have conducted a systematic review to determine whether acute experimental inflammation is associated with changes to cognitive and emotional processing that are thought to cause and maintain depression.MethodsWe identified experimental studies in which healthy individuals were administered an acute inflammatory challenge (bacterial endotoxin/vaccination) and standardised tests of cognitive function were performed.ResultsFourteen references were identified, reporting findings from 12 independent studies on 345 participants. Methodological quality was rated strong or moderate for 11 studies. Acute experimental inflammation was triggered using a variety of agents (including endotoxin from E. coli, S. typhi, S. abortus Equi and Hepatitis B vaccine) and cognition was assessed over hours to months, using cognitive tests of i) attention/executive functioning, ii) memory and iii) social/emotional processing. Studies found mixed evidence that acute experimental inflammation caused changes to attention/executive functioning (2 of 6 studies showed improvements in attention executive function compared to control), changes in memory (3 of 5 studies; improved reaction time: reduced memory for object proximity: poorer immediate and delayed memory) and changes to social/emotional processing (4 of 5 studies; reduced perception of emotions, increased avoidance of punishment/loss experiences, and increased social disconnectedness).ConclusionsAcute experimental inflammation causes negative biases in social and emotional processing that could explain observed associations between inflammation and depression.