 This is largely due to research showing that those with inflammatory conditions like arthritis are more likely to develop mental health problems like depression. Conversely, those who suffer from mental health problems even in the absence of inflammatory conditions have large amounts of inflammatory molecules in the blood. Studies in animals suggest that inflammation outside the brain can reach and affect the brain in a number of ways. So, does inflammation play a role in the development of cognitive and behavioural symptoms? What are the pathways involved? 