Study Title and Description
Caffeine expectancies influence the subjective and behavioral effects of caffeine.
Key Questions Addressed
|1||For [population], is caffeine intake above [exposure dose], compared to intakes [exposure dose] or less, associated with adverse effects on behavior*?|
Primary Publication Information
|Title||Caffeine expectancies influence the subjective and behavioral effects of caffeine.|
|Author||PT Harrell,LM Juliano,|
Secondary Publication Information
There are currently no secondary publications defined for this study.
Extraction Form: Behavior - Design Details - INCLUDED Studies
No arms have been defined in this extraction form.
|Question... Follow Up||Answer||Follow-up Answer|
|What outcome is being evaluated in this paper?||Behavior|
|What is the objective of the study (as reported by the authors)?||This study investigated the independent and interactive effects of caffeine pharmacology and expected effects of caffeine on performance and subjective outcomes.|
|Provide a general description of the methods as reported by the authors. Information should be extracted based on relevance to the SR (i.e., caffeine related methods)||Folgers decaffeinated coffee (22 g) was prepared with 500 ml of water using a drip coffee maker. Independent laboratory analysis indicated that this coffee typically contains approximately 11 mg of caffeine per 12 oz serving (University of Florida College of Medicine Forensic Toxicology Laboratory, Gainesville, Florida, USA). Based on prior randomization and in double-blind fashion, the experimenter added 28 ml of solution that was either a 1:10 mixture of caffeine anhydrous (Sigma-Aldrich Foundation, St Louis, Missouri, USA) and water (i.e., 280 mg caffeine) or flattened tonic water (0 mg caffeine). On the experimental day, participants provided a saliva sample, and then completed self-report measures (task–specific caffeine expectancies, coffee urge, profile of mood states (POMS), caffeine withdrawal, and negative somatic effects) and the RVIP and finger tapping tasks. They were then given a 12-ounce cup of coffee that contained either 280 mg caffeine or placebo.Caffeine dose was crossed with varying instructions that the coffee would either enhance or impair performance in a 2×2 factorial design. Self-report measures included a 28-item questionnaire assessing demographic information and a 16-item caffeine exposure questionnaire that assessed total daily exposure to caffeine (in milligrams). Three measures all using 5-point Likert scales from "0" ("Not at all") to "4" ("Extremely") were administered throughout the study: (1) profile of mood states–short form, a 30-item measure of mood (Curran 1995; McNair et al. 1992) with six factors: tension–anxiety, depression–dejection, anger–hostility, vigor–activity, fatigue–inertia, and confusion–bewilderment (confusion–bewilderment was not analyzed due to poor internal consistency, i.e., Cronbach alpha = 0.58); (2) caffeine withdrawal symptom questionnaire (CWSQ), the sum of 23-item reflective of caffeine withdrawal (e.g., headache, fatigue, and irritability; alpha=0.88); and (3) negative somatic effects, the sum of the following ten self-reported symptoms: headache, blurred vision, flu-like feelings, heavy feelings in arms and legs, upset stomach, nausea/vomiting, muscle pain/stiffness/aches, hot or cold spells, jittery, and rapid heartbeat (alpha=0.81). A 3-item coffee urge measure derived from the questionnaire of smoking urges (Kozlowski et al. 1996) was used to assess urge to consume coffee using a 7-point Likert scale from "1" ("Strongly disagree") to "7" ("Strongly agree") (alpha=0.92).|
|How many outcome-specific endpoints are evaluated?||4|
|What is the (or one of the) endpoint(s) evaluated? (Each endpoint listed separately)||tension-anxiety|
|List additional health endpoints (separately).|
|List additional health endpoints (separately)|
|What is the study design?||Controlled Trial|
|Randomized or Non-Randomized?||RCT|
|What were the diagnostics or methods used to measure the outcome?||Subjective|
|Optional: Name of Method or short description||POMS questionnaire|
|Caffeine (general)||Caffeine (general)|
|What was the reference, comparison, or control group(s)? (e.g. high vs low consumption, number of cups, etc.)||placebo vs. 280 mg caffeine|
|What were the listed confounders or modifying factors as stated by the authors? (e.g. multi-variable components of models. Copy from methods)||None listed|
|Provide a general description of results (as reported by the authors).||There were no significant caffeine dose main effects for any of the subjective measures.|
|Did the authors perform a dose-response analysis (or trend/related analysis)?||No|
|What were the authors's observations re: trend analysis?|
|What were the author's conclusions?||There were no significant main effects for caffeine dose on subjective outcomes. This could be a result of decaffeinated coffee producing effects similar to caffeinated coffee due to conditioned effects and/or expectancy effects as all participants were exposed to coffee and were told that the coffee was caffeinated (e.g., Flaten and Blumenthal 1999; Mikalsen et al. 2001)|
|What were the sources of funding?||Not reported|
|What conflicts of interest were reported?||Not reported|
|Does the exposure (dose) need to be standardized to the SR?||No|
|Provide calculations/conversions for the exposure based on the decision tree in the guide (for all endpoints/exposure levels of interest).|
|List all the endpoint(s) followed by the dose (mg) which will be used in comparison to Nawrot. Characterize value as LOAEL/NOAEL, etc. if possible.||tension-anxiety NOAEL = 280 mg depression-dejection NOAEL = 280 mg anger-hostility NOAEL = 280 mg fatigue-inertia NOAEL = 280 mg|
|Notes regarding selection/listing of endpoints and exposures/doses to be compared to Nawrot.||Only one exposure level (280 mg) was included in the experimental design|
|What is the importance of the study with respect to the adverseness of the outcome?||Important|
No baseline characteristics have been defined for this extraction form.
Results & Comparisons
No Results found.
|Arm or Total||Title||Description||Comments|
No quality dimensions were specified.
No quality rating data was found.