[The influence of psychological factors on the immune system and immunological diseases]

During the last 10-20 years it has become clear that the immune system not only protects the individual against potentially harmful intruders but also interacts with both the nervous and endocrine systems. Today we know that immune competent cells have receptors for hormones and neurotransmitters, and that cytokine receptors are expressed in certain areas of the brain. Furthermore, in many animal models immune suppression has been induced by classical conditioning. Several in vitro studies have shown signs of reduced immunity in individuals during acute and chronic stress. Some studies have also indicated that chronic stress may increase the risk of infections and cancer. On the other hand, various psychotherapeutic techniques appear to strengthen the immune system. As for immunological disease, we know that psychological factors are important in the case of allergic asthma. Moreover, serious life events prior to onset of disease are reported more frequently by seronegative than by seropositive rheumatoid arthritis patients. Prospective studies have shown that psychotherapeutic intervention can reduce disability in rheumatoid arthritis patients, but disease activity is diminished only rarely.