Neurológia pre prax 5/2012

The neuropsychiatric basis of placebo/nocebo phenomena

Due to advances in imaging technology (PET, fMRI) and neuropsychopharmacological knowledge, there has been a shift in the understanding of the ancient phenomena of "placebo and nocebo" from empirical to a more scientifically exact level with surprising findings. Both the phenomena have neurotopically distributed territories, neurotransmitter coverage (particularly with the opioid, dopamine, and cholecystokinin systems). The placebo effect may be inhibited by naloxone while the nocebo phenomenon by using proglumide. The mechanisms accepted in these reactions are the processes of expectation (of a reward) as well as complicated Pavlov's principles of conditioning. There still remain a number of unexplained or unresolved problems (e.g. responsiveness to these phenomena, nonstandard nature and transience of their manifestations). The placebo/nocebo phenomena are most significantly involved in a range of neuropsychiatric affections. The current state of knowledge confirms the irreplaceability of placebo use in objectification of the effect of novel therapeutic molecules in a randomized double-blind trial. A dramatic increase in information in this field might even result in the establishment of a separate subspeciality – "placebology".

Keywords: placebo, nocebo, opioid system, dopamine, serotonin, cholecystokinin system, panic disorder, naloxone, proglumide, mechanisms of reward and conditioning, "placebology".