Éimear Foley discusses a new systematic review examining links between inflammation and depression.
Depression is an illness that is estimated to affect around 10-20% of the world’s population in a lifetime. However, for many people, current treatment strategies do not work sufficiently well. Depression is a multifactorial condition and there is mounting evidence that several biological and non-biological mechanisms may be at play.
One aetiological factor of increasing interest is inflammation. Prof Golam Khandaker, Head of the Immunopsychiatry Programme at the University of Bristol’s MRC Integrative Epidemiology Unit, tries to illustrate this point by asking people to think of the symptoms they experience when they have a cold or flu. Along with a runny nose and a cough, people often experience fatigue, a change to usual appetite or sleeping patterns, and/or a reduced ability to experience pleasure. He points out that these are also typical symptoms of major depressive disorder. Moreover, were you to have a blood sample taken, you would also find evidence of high levels of inflammation due to the activation of an immune response. Recent research suggests that up to a quarter of all depressed patients consistently show evidence of inflammation in their blood, as defined by C-reactive protein levels. Other studies have supported these findings, showing that depression may be causally linked to elevated concentrations of proinflammatory cytokines (i.e., proteins often used as markers of inflammation), like interleukin 6.