Positive emotional states and enhancement of the immune system.

Salivary immunoglobulin A (IgA) concentration increased significantly after subjects viewed a humorous videotape and did not change significantly after they viewed a didactic videotape. Scores on a questionnaire measuring the perceived use of humor as a coping skill were positively related to initial IgA concentration and inversely related to changes in IgA concentration after subjects' viewing of the humorous videotape, which implies a ceiling effect. Enhancement of the immune system may be one link between anecdotal claims of relationships between an individual's being in a positive emotional state and healing.