The Immune System The Culprit Behind Depression
Depression is the pathological equivalent of normal sadness, a somber, disagreeable felling, that qualitatively differs from normal sadness by its pathological intensity, duration, type of occurrence and reactivity. Depression is affecting one in ten adults, regardless of gender, making researchers believe depression is deeply rooted in the human brain. This assumption has made scientists believe that depression may be in fact actually an advantage in evolutionary terms.
Until now, researchers only studied how depression is affecting social behavior and which is the evolutionary role of this disease. A recent study conducted by scientists from the Winship Cancer Institute and from the University of Arizona revealed that between depression and inflammation (produced by the immune system) certain connection exist, making them to believe that throughout evolution, depression which is caused by some genetic variations can represent a defense mechanism that helped our ancestors fight infection. This study was published in the journal Molecular Psychiatry.
“Most of the genetic variations that have been linked to depression turn out to affect the function of the immune system. This led us to rethink why depression seems to stay embedded in the genome.”, said the leader of researchers team.
With this study researchers found that between depression and inflammation (as a result of the over-stimulation of the immune system) a certain link. The idea is supported by the fact that depressive patients present an increased inflammatory activity, in the absence of infection. It also very important to note that high levels of inflammatory markers are not a consequence of depression.
Before mankind discovered antibiotics, the main cause of death was infection. The human body responded and fought infection resorting to some behavioral changes which are similar to depression symptoms. Scientists believe that in addition to immune responses emerged for controlling an infection certain depressive symptoms like fatigue, inactivity, anorexia and social avoidance are also present. It is thought that these ‘defence mechanisms’ are designed to limit the transmission of infection.
This new hypothesis may explain why stress is a risk factor for depression because researchers now think that depression and stress are interconnected and are seen as a mechanism that can activate the immune system in anticipation of an injury. It was observed that changes in sleep patterns, symptoms that are found both in depression and stressed patients can activate the immune system.
This new hypothesis has important clinical relevance as scientists now believe that by measuring inflammatory markers they will be able to assess depression treatment response. Researchers also hope that their findings will lead to new treatment options for patients suffering from treatment-resistant depression, making use of drugs that are currently prescribed for treating autoimmune diseases.