Skip to main content

Table 3 Drug, placebo, placebo+interaction, and total effects on self-classification as not-energetic, sleepy, and nauseated.

From: Interaction between drug and placebo effects: a cross-over balanced placebo design trial

 

Drug

Effect

Placebo

Effect

Placebo+

interaction

Effect

Total

Effect

Not-energetic

-6.3 [-15.4 to 2.8]

P = 0.09

-7.9 [-14.5 to -1.3]

P = 0.01

-2.4 [-7.8 to 3.0]

P = 0.19

-8.6 [-17.5 to -1.7]

P = 0.03

Sleepy

-12.9 [-23.1 to -2.6]

P = 0.007

-7.9 [-16.4 to 0.0]

P = 0.03

-3.1 [-10.4 to 4.1]

P = 0.19

-16.0 [-26.2 to -5.8]

P = 0.001

Nauseated

-2.1 [-8.1 to 3.8]

P = 0.24

-3.4 [-8.8 to 1.9]

P = 0.10

1.2 [-3.8 to 6.3]

P = 0.32

-0.9 [-7.3 to 5.5]

P = 0.39

  1. Data are mean [95% confidence interval] percentage of time the particular symptom was reported over 4 hours after intervention.
  2. P values are from 1-tailed t test. Drug effect = "receiving caffeine described as placebo" mean - "receiving placebo described as placebo" mean. Placebo effect = "receiving placebo described as caffeine" mean - "receiving placebo described as placebo" mean. Placebo+interaction effect = "receiving caffeine described as caffeine" mean - "receiving caffeine described as placebo" mean. Total effect = "receiving caffeine described as caffeine" mean - "receiving placebo described as placebo" mean. Mean(SE) percentage of time not-energetic, sleepy, or nauseated, respectively, were reported over 4 hours after intervention were 10.0(2.6), 15.9(3.2), and 7.6(2.1) when caffeine was described as caffeine; 12.4(2.9), 19.0(3.3), and 6.3(1.7) when caffeine was described as placebo; 18.6(3.6), 31.9(4.1), and 8.5(2.4) when placebo was described as placebo; and 10.8(2.7), 24.0(3.5), and 5.0(1.1) when placebo was described as caffeine.