Effects of Inflammation on Affect and Emotion: A Systematic Review of Experimental Studies

Mental illness poses a substantial public health burden in the United States, highlighting the importance of understanding the biological mechanisms and risk factors underlying its development. Previous research has increasingly linked mental illness, particularly depression, with elevated inflammatory markers. Experimental paradigms using lipopolysaccharide (LPS) and vaccine-induced inflammation have allowed for the causal investigation of inflammation’s effects on affect, mood, and emotion. This systematic review synthesizes current findings on inflammation-induced affective changes in humans. Analysis of 24 studies in this area revealed that the majority of studies report significant increases in negative affect following an inflammatory challenge, with depressed mood being the most consistently measured and observed outcome. LPS studies produce the most reliable increases in negative affect compared to vaccine paradigms. However, further research is needed to clarify the biological mechanisms linking inflammation and psychopathology, ultimately supporting the development of more effective psychological treatments and improving risk assessment for individuals with chronic inflammation.