What You Think Can Make You Sick: Dr. Robert Ader Who Showed That The Brain Affects The Body's Immune Response How We React to Disease"The man who helped discover that what's in your mind can literally make you sick has passed away. His study, clearly demonstrated that immune responses (such as antibody production) could be modified by classical conditioning, showing that there were connections between the brain and the immune system (the immune system protects the body against infection with antibodies among other defenses) and that the mind could have profound effects on the body’s functions that were thought to be independent.
In the early 1970s, in what would become one of his most distinctive experiments, Dr. Ader was studying taste aversion conditioning in rats. In the experiment, rats drank different volumes of a saccharin solution and also were injected with a dose of Cytoxan, an immunosuppressive drug that induces gastrointestinal upset. The rats “learned” or were conditioned to avoid consuming the solution.
When he stopped giving the rats the drug but continued to give them the saccharin solution, not only did the rats avoid drinking the solution, some of the animals died.
link to Robert Ader, Founder of Psychoneuroimmunology