Positive Health Online

Abstract

WALACH and colleagues, Universitaetsklinikum Freiburg, Institut fuer Umweltmedizin und Krankenhaushygiene, Hugstetterstrasse 55, 79106 Freiburg, Germany, walach@ukl.uni-freiburg.de, investigated the effects of suggestion and expectation on cardiovascular responses, feeling of wellbeing and a cognitive task.

Background

Methodology

In this randomized, controlled clinical study, 159 subjects received either a caffeine placebo or served as controls. Subjects were randomized to one of two conditions. Condition 1 was identical to that used in an earlier study. In condition 2, subjects were given information about the scientifically proved effects of caffeine (factor 1) and also received varied instructions (factor 2). Factor 2 instructions comprised: either instructions to subjects to expect coffee, no coffee or placebo; or subjects were in a double-blind condition and were told that they would receive either coffee or placebo. Study measurements included: recordings of blood pressure and heart rate; measures of wellbeing; and scores on a cognitive task.

Results

The single main effect was that of the instruction factor on diastolic blood pressure (DBP): subjects who were told they would receive coffee showed a significantly smaller decrease in DBP than controls or subjects in the double-blind condition.

Conclusion

The ‘placebo-caffeine’ paradigm used in the present study appears to be unsuitable for researching instruction effects, as least in Germany. Instruction effects need to be reexamined using tighter controls in order to confirm instruction effects reported elsewhere.

References

Walach H et al. The effects of a caffeine placebo and suggestion on blood pressure, heart rate, well-being and cognitive performance. International Journal of Psychophysiology 43 (3): 247-60. Mar 2002.

Comment

This shows how tricky paradigms and beliefs can be, and how important it is to test methodology while conducting research.