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Study Title and Description

Caffeine expectancies but not caffeine reduce depletion-induced aggression.



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*?
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Primary Publication Information
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TitleData
Title Caffeine expectancies but not caffeine reduce depletion-induced aggression.
Author TF Denson,M Jacobson,W von Hippel,RI Kemp,T Mak,
Country
Year 2012
Numbers

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Extraction Form: Behavior - Design Details - INCLUDED Studies
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Design Details
Question... Follow Up Answer Follow-up Answer
Refid 21766974
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What outcome is being evaluated in this paper? Behavior
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What is the objective of the study (as reported by the authors)? The present research examined the influence of caffeine and caffeine expectancies on depletion-induced aggression.
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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) Experiment 1: A total of 113 undergraduates from the University of New South Wales participated in a study ostensibly investigating the effects of caffeine on impression formation and executive functioning. Data were excluded because of suspicion that the provocation was fabricated (n=_x0001_ 6) or software failure (n=10), leaving a final sample of 96 participants (38 men) who were randomly assigned to one of four conditions in a 2 (caffeine, placebo) x_x0002_ 2 (depletion, no-depletion) between participants design. The items energized, excited, jittery, alert, and vigorous constituted a stimulation subscale (_x0004_ a= .63) and irritable, hostile, and annoyed constituted an anger subscale (_x0004_a=.72; 1 _x0001_ not at all, 7 _x0001_ extremely so). The two subscales were uncorrelated, r= .17, p= .11. Participants in the caffeine condition received a 200-mg caffeine tablet. Those in the placebo condition received a sucrose tablet (containing _x0005_1 g sucrose) administered from the same clearly labeled bottle as the caffeine tablets in order to appear as if they were actually receiving caffeine. Participants were told that they were receiving a dose equivalent to drinking 2 cups of coffee. Because caffeine absorption reaches 99% in approximately 45 min (Lorist & Tops, 2003), participants were asked to return 45 min later. Participants completed the second mood questionnaire upon return to the laboratory: stimulation,_x0004_ a=0.79; angry affect, a=0.79. Aggressive behavior was operationalized as the mean intensity and duration of a blast of white noise participants selected to deliver to the bogus participant during a modernized single-trial version of the Taylor (1967) Aggression Paradigm (TAP; e.g., Bushman, 1995; Denson et al., 2010). The noise levels ranged from 1 (60 dB) to 10 (105 dB), and durations ranged from 0 (0.5 s) to 10 (1.75 s). A nonaggressive 0 dB option was also included. Extensive research supports the validity of the TAP; individuals who report engaging in aggression and violence outside the laboratory behave more aggressively in studies using the TAP (Anderson & Bushman, 1997; Bernstein, Richardson, & Hammock, 1987; Carlson, Marcus-Newhall, & Miller, 1989; Giancola & Chermack, 1998; Giancola & Parrott, 2008; Giancola & Zeichner, 1995; Hammock & Richardson, 1992). Participants rated their mood following the TAP for the third time: stimulation, a= _x0001_ .80; angry affect a= .72. They were then probed for suspicion and debriefed. Experiment 2: A total of 133 undergraduates from the University of New South Wales participated. Nine participants’ data were removed because of suspicion regarding the provocation manipulation, leaving a total of 124 participants (63 men; age=_x0001_ 19.75 years, SD=_x0001_ 2.12). All participants reported compliance with the 48-hr washout period and were randomly assigned to conditions in a 2 (depletion, no-depletion) x_x0002_ 3 (caffeine, placebo, no-pill control) between-participants design. The caffeine and placebo procedures were the same as in Experiment 1, as was the depletion manipulation. Control participants who did not receive a pill were able to immediately proceed with the experiment. Prior to the depletion manipulation, participants in all conditions rated how they were currently feeling with a mood adjective checklist consisting of 24 items measuring positive affect (e.g., happy; a=_x0004__x0001_.81), general negative affect (e.g., sad; a=_x0001_ .91), and the three angry affect items from Experiment 1 (_x0004_a= .85; 1 = not at all, 7 = extremely so). Participants completed the same provocation procedure and aggression paradigm from Experiment 1 and then reported on their mood as a result of the video conference using the checklist: positive affect, a=_x0001_ .81; negative affect, a=_x0001_ .81; and angry affect, a =_x0001_ .93. Finally, the experimenter probed for suspicion and debriefed participants.
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How many outcome-specific endpoints are evaluated? 2
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What is the (or one of the) endpoint(s) evaluated? (Each endpoint listed separately) Aggression
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List additional health endpoints (separately).
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List additional health endpoints (separately)
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Notes Aggression was assessed after mental depletion from an administered task
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Clinical
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Physiological
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Other
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What is the study design? Controlled Trial
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Randomized or Non-Randomized? RCT
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What were the diagnostics or methods used to measure the outcome? Both
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Optional: Name of Method or short description Aggression was measured by Taylor Aggression Paradigm (TAP), which allows subjects to control intensity and duration of a white noise blast. Anger was measured using an unspecified questionnaire
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Caffeine (general) Caffeine (general)
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Coffee
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Chocolate
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Energy drinks
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Gum
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Medicine/Supplement
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Soda
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Tea
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Measured Measured
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Self-report
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Children
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Adolescents
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Adults Adults
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Pregnant Women
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What was the reference, comparison, or control group(s)? (e.g. high vs low consumption, number of cups, etc.) Experiment 1: Placebo compared to 200 mg caffeine Experiment 2: No-pill control compared to placebo or 200 mg caffeine
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What were the listed confounders or modifying factors as stated by the authors? (e.g. multi-variable components of models.  Copy from methods) Nothing specific was mentioned however study authors included a footnote stating an interaction retained statistical significance when controlling for gender.
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Provide a general description of results (as reported by the authors). Experiment 1: Simple effects analyses revealed that when participants were depleted, those who consumed the placebo were marginally less aggressive than those who consumed caffeine, F(1, 45)= 3.22, p=0.08). No differences were found between caffeine and placebo when participants were not depleted. Among participants given placebo, those who were depleted did not reliably differ in aggression from participants who were not depleted (p= .33). Participants given caffeine were more aggressive when depleted than when not depleted, F (1,46) = 7.17, p= .01. ANOVA revealed no main effects or interaction on angry affect at the third assessment (Fs <_x0005_ 1), Experiment 2: Participants who consumed caffeine and were depleted were as aggressive as those in the depletion/no-pill condition, F< 1, suggesting that caffeine does not decrease depletion-induced aggression. When not depleted, participants given caffeine were more aggressive than participants not given a pill, F(1,36)=_x0001_ 7.79, p =_x0001_ .008, suggesting an excitation transfer effect. Replicating Experiment 1, among nondepleted participants, levels of aggression for those given the placebo did not differ from those in the caffeine condition, F<1.
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Did the authors perform a dose-response analysis (or trend/related analysis)? No
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What were the authors's observations re: trend analysis?
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What were the author's conclusions? Relative to caffeine, consuming a pill that is believed to contain caffeine prior to engaging in demanding menta lactivity reduced provoked aggression. The primary result is clear across the two experiments: Caffeine led to greater aggression than placebo in the depletion conditions and no difference from placebo in the no depletion conditions. Experiment 2 introduced a no-pill control condition. Caffeine increased aggression relative to no pill only when not depleted. Thus, caffeine had no additional effect on aggression beyond that of depletion. These results clarify the findings of Experiment 1 by demonstrating that caffeine does not increase aggression when depleted, but rather that the placebo reduces aggression when depleted.
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What were the sources of funding? This research was supported by a Discovery Project grant from the Australian Research Council to Thomas F. Denson.
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What conflicts of interest were reported? None reported
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Does the exposure (dose) need to be standardized to the SR? No
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Provide calculations/conversions for the exposure based on the decision tree in the guide (for all endpoints/exposure levels of interest).
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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.  Aggression NOAEL = 200 mg Anger affect NOAEL = 200 mg
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Notes regarding selection/listing of endpoints and exposures/doses to be compared to Nawrot. This study only administered one exposure level of caffeine.
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What is the importance of the study with respect to the adverseness of the outcome? Low
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