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document
The influence of placebo awareness on stimulant drug response in a double-blind trial . RATIONALE Critics have called into question findings from double-blind placebo-controlled studies because subjects are given drug administration instructions informing them of a placebo condition . The assertion that these drug administration instructions bias estimates of effectiveness has undergone surprisingly little empirical investigation . OBJECTIVES The primary objective of this study was to determine whether drug administration instructions informing subjects of a placebo condition affect the drug response and affect the saliva concentration of the stimulant . METHODS We assessed caffeine responses and levels of saliva concentration of caffeine in 52 subjects who were randomly assigned to receive one of two drug administration instructions : ( a ) placebo-informed instructions ( i.e. , individuals informed of the placebo ) analogous to those used in double-blind studies and ( b ) placebo-uninformed instructions ( i.e. , individuals informed they are taking an active stimulant ) . RESULTS On most measures ( systolic blood pressure , heart rate , hand steadiness , reaction time , fatigue , and tension ) , drug administration instructions did not significantly influence caffeine response . Instructions also had no significant effect on saliva concentration of caffeine . However , only individuals who were uninformed of the placebo condition showed significant diastolic blood pressure and vigor increases with 125 mg caffeine , and significant hand steadiness impairment and vigor increases with 325 mg caffeine compared to placebo . CONCLUSIONS These overall findings suggest that a limited bias is introduced by drug administration instructions . The results do not support any suggestion that information about the existence of a placebo condition dramatically influences conclusions drawn about drug responses in placebo-controlled trials .
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Intervention_Psychological
placebo
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Intervention_Psychological
placebo-informed instructions
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Intervention_Psychological
individuals informed of the placebo
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Intervention_Psychological
placebo-uninformed instructions
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Intervention_Educational
individuals informed they are taking an active stimulant
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Intervention_Pharmacological
caffeine
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Intervention_Pharmacological
caffeine
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Outcome_Physical
saliva concentration
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Outcome_Physical
caffeine responses and levels of saliva concentration of caffeine
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Outcome_Physical
( systolic blood pressure , heart rate , hand steadiness , reaction time , fatigue , and tension )
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Outcome_Physical
caffeine response
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Outcome_Physical
saliva concentration
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Outcome_Physical
diastolic blood pressure and vigor
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Outcome_Physical
hand steadiness impairment and vigor
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Participant_Condition
caffeine responses and levels of saliva concentration of caffeine