Pavlov revisited. About the placebo effect of rose scent
Health psychologist Aleksandrina Skvortsova has made clever use of the Pavlov effect to link the ‘cuddle’ hormone oxytocin with the placebo effect. This effect can alter the level of oxytocin in the body, making it possible for people to reduce the amount of medicine they need while still feeling good. This finding offers good prospects for treating patients with mental disorders. PhD defence 29 October.
In her PhD research on the placebo effect, Skvortsova made use of the Pavlov effect. You know the one: the dog that salivates when it hears a bell because it connects the bell with food. In her research, Skvortsova has linked the cuddle hormone oxytocin to a relatively unique rosewood scent. At the same time as smelling this scent, the participants were administered the hormone oxytocin, which produces a feeling of pleasure. After a while, the scent alone was enough to produce that pleasant feeling. Just as the dog in the Pavlov effect produced saliva, the participants were shown to produce oxytocin themselves.
Oxytocin and rose scent
However, the production of oxytocin in response to the rose scent did lessen and come to a halt. After three days, with participants only smelling the scent and not receiving any hormone, no traces of the hormone could be detected in the saliva of the healthy women taking part. Skvortsova suspects that this decline in the production of oxytocin may explain why she did not find any effect on the brain activity of the participants while in the MRI scanner: the participants only reported to the LUMC for a brain scan at the end of the research. Skvortsova had expected to detect extra activity in the brain areas that are sensitive to oxytocin, such as the amygdala, but there was no evidence of increased activity.
Combining placebo effect with medicines
Placebo effects can trigger changes in the hormone system, but have previously only been tested in humans in combination with the hormones insulin, cortisol and human growth hormone. Skvortsova has now included conditioning for the hormone oxytocin in her study. As this hormone reduces stress and anxiety, she sees good prospects for treating people with mental conditions. She believes placebo effects are very promising for clinical practice. At the same time, she wants to reassure sceptics: ‘The placebo effect never replaces medicines, but is used in combination with medicines.’ Reducing the use of medicines obviously means lower costs and also fewer side-effects.
Pain and itching
In the second part of her dissertation, Skvortsova tested placebo effects with pain and itching. Because oxytocin reduces stress and increases confidence, it could also increase the placebo effect in pain and itching. Hormones work differently for men and women, so Skvortsova explored this in two studies: first with healthy women and then with healthy men. She found no effect in either of the two studies. ‘Other researchers will have to find different ways of increasing the placebo effect.’
Telling stories about science
Skvortsova made a video about her placebo research, which can be viewed on 'Scientist Wanted', a platform for telling interesting stories about science. She is now examining the possibilities of conditioning diabetes patients for insulin. This is also something she is happy to talk about in her video.
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This PhD research is part of the ERC Consolidator grant of Andrea Evers