It is now well established that there are links between the brain and the immune system. A whole field, called psychoneuroimmunology, devotes itself to the study of how these systems are interconnected. The term psychoneuroimmunology was coined by Robert Ader and Nicholas Cohen, two scientists who were able in 1975 to show that it was possible in rats to couple a sugary drink (unconditioned stimulus) to an immune-suppressing drug (conditioned stimulus), and then use the sugary drink to induce immune suppression.
Immune modulation by behavioural conditioning
A paper published last year in the journal Psychotherapy and Psychosomatics shows that the antiallergic effects of antihistamines can be behaviourally conditioned in humans. Marion Goebel and co-workers recruited patients with allergic rhinitis and divided them into three groups. All three groups got an antihistamine coupled with a novel-tasting drink daily for five days. Then, after allowing some time so no antihistamine would remain in the body, the experiment started.
One group got the novel-tasting drink with a placebo pill, one group got a glass of water with a placebo pill, and the third group got a glass of water with the real antihistamine. The authors then measured subjective symptoms, skin prick reaction and the activation of white blood cells known as basophils.
The group that got just water and a placebo pill did show a reduction of symptoms and skin prick test reaction, but not of basophil activation. The group that got the real antihistamine had a reduction in all three measures. Interestingly, the group with the novel-tasting drink an placebo pill also showed improvement on all three counts, to levels comparable to the drug group!
Work with the brain – that’s where the memory is
In humans, it has been known for some time that allergic responses can be fairly easily conditioned. Perhaps that is one reason why some people have strange allergic symptoms to things like electric fields, which cannot possibly induce allergies. (In fact, is has been shown that it’s not the electric field itself that does it, but rather the sensation of being in an electric field. The condition of electromagnetic hypersensitivity can be very disabling – the symptoms are real even though the biological foundation isn’t there.)
The present study suggests that antiallergic effects can also be conditioned. For a humble young physician like myself, it’s a useful reminder that the drugs we prescribe often don’t work the way we think they do.
Goebel, M., Meykadeh, N., Kou, W., Schedlowski, M., & Hengge, U. (2008). Behavioral Conditioning of Antihistamine Effects in Patients with Allergic Rhinitis Psychotherapy and Psychosomatics, 77 (4), 227-234 DOI: 10.1159/000126074