When one cup is not enough: The effects of caffeine consumption, tolerance and withdrawal on an individual’s energy levels.
Caffeine is the worlds most popular psychoactive compound, Consumed on a daily basis by 80% of the worlds population (James & Keane, 2007; Rogers, Heatherly, Mullings & Smith, 2013). It has long been believed that caffeine has physiologically enhancing properties and is often used to help increase in energy levels (James & Keane, 2007). Drug tolerance is defined as the reduction in the effect of a given dose of a drug less than the original, after repeated administrations (Siegel, 1975).
There are multiple theories on tolerance, which will be used in this study to ...view middle of the document...
. As caffeine increases arousal levels, it was predicted that… The decaf condition would report a decrease in energy levels greater than that of reported by rooibos condition.
One thousand and sixty-one undergraduate students at the University of Western Australia participated as a course requirement of the first year Psychology 1101. Participants randomly assigned into three groups and instructed that voluntary withdrawal was allowed at any time.
Participants were asked a series of five pre-questions asserting age, gender, average daily caffeine consumption; caffeine consumption on the day of the experiment and current energy levels on a scale to zero (not at all energetic) to 10 (extremely energetic).
Participants were assigned an unlabeled polyurethane cup containing one of three conditions: Coffee, Decaffeinated Coffee or Rooibos tea. One tablespoon of coffee or decaf was added to two of the three groups and one Rooibos tea bag in other. Each condition was mixed with one cup of freshly boiled water from a kettle at the preparation station. Ratings of age etc. were recorded on a piece of paper and communicated to the tutor at the end of the tutorial.
Prior to group allocation, participants completed pre-procedure questionnaire. A double blind study, conditions were randomly assigned. Participants were instructed to refrain from tasting until all conditions had been distributed.
After allocation each group was instructed that they had a time limit of five minutes to consume their beverages, again it was explained that voluntary withdrawal from the experiment at any time was acceptable.
Post consumption, a time window of twenty minutes was observed to allow each condition to take an effect. Each group was then instructed to complete post-procedure questionnaire, self-reporting current energy levels on a scale of zero (not at all energetic) to 10 (extremely energetic).
Descriptive statistics summarizing levels of caffeine consumption and related energy levels are presented in Table 1. The difference in mean (M) values relative to variability (SD) in the scores was of significant value (Cohen’s d=1.08). Signifying large effect size and variation between groups. The difference between groups may be attributed to the significant difference in the Low consumer group (N=348) and the High consumer group (N=27), accounting for a variance in standard error (SE).
Means (SD) for change in energy levels of low consumers of caffeine vs. high consumers of caffeine
M SD SE
Low consumers 2.93 1.97 1.06
High consumers 1.14 1.49 0.29
Table 2 presents the descriptive statistics for all three-drink conditions- Caffeinated, Decaffeinated and Rooibos (control). The difference in mean values for the three conditions is quite small, the largest...