Human ability to experience emotions is evolutionary and genetically determined. The presence of feelings designed to influence behaviour is reflected in physiological and immune interactions. Emotions are involved in the initiation or progression of cancer, HIV, cardiovascular disease, and autoimmune disorders. Specific physiological responses induced by pleasant stimuli were recently investigated with the immune and endocrine systems being monitored when pleasant stimuli such as odors and emotional pictures were presented to objects. The results revealed that an increase in secretory immunoglobulin A and a decrease in salivary cortisol were induced by pleasant emotions.
The mechanisms by which positive as opposed to negative states are instantiated in the brain and interact with the immune system are not yet understood. The present review investigates relations hips between the physiological responses of the affective style, psychological wellbeing (hedonic and eudaimonic) and immune function. There is data to support the hypothesis that individuals characterized by a more negative affective style poorly recruit their immune response and may be at risk for illness more so than those with a positive affective style.