Placebo effect on cognitive performance after conditioning to caffeine supplementation

• Grant number: 22/10973-5
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: October 01, 2022
• End date: September 30, 2023
• Field of knowledge: Health Sciences - Physical Education
• Principal Investigator: Bryan Saunders
• Grantee: Caio Muraca de Azevedo
• Host Institution: Faculdade de Medicina (FM). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Associated research grant: 21/06836-0 - Placebo in sports and exercise: prevalence, conditioning and open-placebo, AP.JP2

Abstract

Historically, placebos are understood as inert interventions, and for this reason, they would not have any kind of effect on the organism. For this reason, placebos started to be used as a comparator in clinical trials, in order to identify the effectiveness of interventions. However, with the advancement of science, it has become clear that the placebo effect is a measurable phenomenon, which can lead to beneficial effects on the body. There are several factors capable of potentiating the placebo effect, such as personality, context, expectation, and, as recent evidence suggests, conditioning. Conditioning is when repeated doses of a certain substance are replaced with a placebo. Studies performed with injectable analgesics such as morphine have identified similar physiological changes between placebos after conditioning and the real substance. Food supplements, especially caffeine, are widely used to improve cognitive performance. The main justification for this effect is the fact that it and its metabolites are antagonists of the adenosine receptors, which leads to an increase in the release of catechol amines, generating increased psychomotor agitation, decreased sleep and tiredness, and, consequently, improved cognitive performance. Although such mechanisms are well established, no studies have evaluated the placebo effect after caffeine conditioning and its responses to cognitive parameters. The hypothesis is that caffeine conditioning potentiates the placebo effect, leading to an improvement in cognitive performance similar to that found with caffeine supplementation, even when the substance is not administered. The present study is associated with a doctoral project and to test this hypothesis, volunteers from the main study will be used, consisting of n = 48 healthy male cyclists, aged 18 to 40 years, with low caffeine consumption. Participants will be randomized into four parallel groups a) No treatment b) Placebo c) Caffeine conditioning d) Conditioning control. For all groups, six visits to the laboratory will be carried out, with two familiarization sessions and four main sessions. In each main visit, volunteers will complete 3 cognitive tests. Questionnaires about expectations, side effects, and food consumption will be applied. Data will be analyzed using a mixed repeated measures model to detect differences in cognitive performance variables.(AU)