Subjective and objective effects of coffee consumption — caffeine or expectations?

Abstract

Impact of 5 mg/kg caffeine, chance of receiving caffeine (stimulus expectancies), and expectations of effects of caffeine (response expectancies) on objective (heart rate (HR), systolic/diastolic blood pressure (SBP/DBP), measures of heart rate variability (HRV), and reaction time (RT)) and subjective variables were investigated in a double-blind, placebo-controlled experiment with a no-treatment group. Participants were 107 undergraduate university students (mean age 22.3 ± 3.96 years). Consumption of 5 mg/kg caffeine had an impact on participants' SBP, standard deviation of normal heartbeat intervals, HR (decrease), and subjective experience 40 minutes later even after controlling for respective baseline values, stimulus and response expectancies, and habitual caffeine consumption. No effects on DBP, high frequency component of HRV, the ratio of low-and high-frequency, and RT were found. Beyond actual caffeine intake, response expectancy score was also a determinant of subjective experience which refers to a placebo component in the total effect. Actual autonomic (SBP, HR) changes and somatosensory amplification tendency, however, had no significant impact on subjective experience. Placebo reaction plays a role in the subjective changes caused by caffeine consumption but it has no impact on objective variables. Conditional vs deceptive administration of caffeine (i.e. stimulus expectancies) had no impact on any assessed variable.

No effects of rosemary and lavender essential oil and a placebo pill on sustained attention, alertness, and heart rate

“…This conclusion may be particularly valid for inhalation, in which case actual levels of active substances in the blood are extraordinarily low. In higher concentrations, an interaction between pharmacological and psychological factors is also conceivable, as in the case of caffeine …”

The Influence of Caffeine Expectancies on Sport, Exercise, and Cognitive Performance

“…Expectancy effects are likely mediated by a variety of factors. Within the current review examples included perceived side effects [ 3 , 6 , 56 , 72 ], habituated expectancies [ 37 , 45 , 46 , 54 , 55 , 56 ], confirmation of successful expectancy manipulation [ 4 , 36 , 37 , 45 , 46 , 56 , 72 , 75 ], pre-existing CAF consumption habits [ 37 , 55 ], and the mode of expectancy manipulation [ 36 , 62 , 72 , 75 , 86 ]. Visual stimuli were always correlated with an expectancy effect [ 36 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 , 66 , 67 , 68 , 69 , 70 , 71 , 72 , 73 , 74 , 75 , 76 , 77 ], irrespective of the performance measure assessed.…”

Investigating the role of expectancy in caffeine withdrawal using the balanced placebo design

“…It is important to note that numerous studies have investigated the role of expectancies in the acute effects of caffeine or used caffeine as a vehicle to investigate placebo effects (e.g., Dömötör, Szemerszky, & Köteles, ; Elliman, Ash, & Green, ; Fillmore & Vogel‐Sprott, ; Flaten & Blumenthal, ; Hammami, Al‐Gaai, Alvi, & Hammami, ; Harrell & Juliano, ; Lotshaw, Bradley, & Brooks, ; Mikalsen, Bertelsen, & Flaten, ; Oei & Hartley, ; Schneider, ; Walach & Schneider, ). However, these studies do not elucidate the role of expectancies in withdrawal symptomatology because they did not assess caffeine withdrawal symptoms, required brief caffeine abstinence (i.e., ≤12 hr) or used nondependent caffeine consumers.…”