Exploring clinical applications of classical conditioning

Pavlov’s dogs are perhaps the most famous case of classical conditioning. In his experiments Pavlov paired the ringing of a bell with presenting his dogs with food, and then he measured the amount of saliva produced by ringing the bell alone. By taking these measurements before and after the pairing, it was shown how a stimulus that normally has no response could be paired with a stimulus that does.

The principles of classical conditioning extend far beyond canines and saliva; they can even be used to condition our immune system as a means of treating autoimmune diseases. Lupus is one such autoimmune disease, and treatment requires the suppression of a person’s immune system to protect their tissues and organs from being targeted by their own white blood cells. Cyclophosphamide is a chemotherapeutic drug taken orally or intravenously that is considered to be the standard treatment for lupus; however, like many chemotherapies, the side-effects of the drug can be quite severe.

In $1992$‍ a team of researchers showed that the human immune system can be classically conditioned, such that an $11$‍ year old girl suffering from lupus was able to have significant reduction of her symptoms without any need of immunosuppressant drugs. This provided an opportunity to treat their patient’s disease while avoiding the deleterious side effects of cyclophosphamide.

For their experiment, the researchers utilized a “Compound CS” which was a liquid that tasted of cod liver oil and had the smell of a rose. They paired Compound CS with the cyclophosphamide treatments on $6$‍ occasions for a year. Every other month of treatment, the researchers did not administer the cyclophosphamide, and simply gave their patient compound CS instead. Despite administering the immunosuppressant drug at half the normal dose, the 11 year old patient still evidenced immunosuppression and continued to do well after a $5$‍ year followup.

*Citation: Giang DW, Goodman AD, Schiffer RB, Mattson DH, Petrie M, Cohen N, Ader R. J Conditioning of cyclophosphamide-induced leukopenia in humans. *
Neuropsychiatry Clin Neurosci. 1996 Spring;8(2):194-201. Cohen N, Ader R. Immunomodulation by classical conditioning. Adv Biochem Psychopharmacol. 1988;44:199-202.