Cognitive dysfunction is proposed to be a feature and risk factor for depression. Evidence from observational and experimental studies suggest a role of low-grade systemic inflammation in depression, which could also be relevant for cognitive dysfunction. Existing cross-sectional studies suggest that inflammation is associated with cognitive dysfunction, particularly poor memory, processing speed, executive function and emotional bias. Limited longitudinal evidence, often based on the elderly population, also suggest a potential link between inflammation and impaired learning, memory, attention, and general cognitive functioning and decline. While these studies point to a potential role of inflammation in cognition, there are key unanswered questions.

First, much of the existing evidence around inflammation and cognition is based on the elderly population, so it is unclear whether inflammation is associated with cognition earlier in the life course. Second, it is unclear whether inflammation plays a causal role in cognitive dysfunction, as cytokine elevation could alternatively be a consequence of cognitive impairment (i.e., reverse causality) or due to confounding. I propose to address these issues using epidemiological approaches.