The cause of depression is not fully understood; however, previous research has suggested that inflammation may be a contributing factor in its development.
Inflammation & Depression
In his book ‘The Inflamed Mind’ professor Edward Bulmore of the University of Cambridge puts forth the theory that inflammation causes depression. He believes that stress is one of the key drivers of inflammatory changes. From a evolutionary perspective acute stress can signal a potential attack and an increased likelihood of injury. For this reason it makes sense for the body to prepare for a wound by increasing inflammation as it plays a key role in repairing a wound that may be incurred from an injury. Bulmore found that blood sample of people who say they are depressed shows a higher level of inflammatory markers than samples from people who are not depressed. Research by Wium-Andersen et al. examined 73 131 men and women aged 20 to 100 years. The blood marker used to measure inflammation in the body is CRP. Elevated levels of CRP are associated with increased risk for psychological distress and depression in the general population. In this study there was a “dose-response” relationship between people who reported low moods and inflammation. Those with greater inflammatory markers had worse moods than those with lower markers. Like most areas of research, not all studies have shown a correlation between inflammation and depression, especially when confounding variables such as body weight are taken into consideration. Interestingly, research in rats has demonstrated that when they are injected with cytokines (proteins that signal inflammation) they become listless and demonstrate behaviours similar to people suffering from depression. In humans, vaccinations, such as those given for tuberculosis, are known to induce an inflammatory response and to induce low mood also. Recent genetic research that certain genes related to inflammation and immune function are also linked to depression.