ABSTRACT

Background:

Experimental studies suggest that caffeine benefits cognitive function, including cognitive control processes such as response inhibition.  However, recent cross-sectional studies purport that caffeine is, alternatively, associated with reduced response inhibition and associated concepts such as increased impulsivity, risk-taking, and aggression. However, such correlational designs, by definition, cannot conclude causal relationships. Thus, the present research employed a quasi-experimental design to explore whether caffeine influences response inhibition, impulsivity, risk-taking, and aggression in both high and low habitual caffeine consumers.

Methods:

Forty-one participants, including 15 high habitual caffeine consumers (caffeine intake >300 mg/ day) and 26 low habitual caffeine consumers (caffeine intake <100 mg/day), consumed 0 mg, 100 mg, 200 mg, 400 mg, and their normal caffeine on each of five separate mornings. They completed trait measures of aggression, impulsivity, and anger, as well as cognitive tasks probing response inhibition, impulsivity, risk-taking, and aggression.

Results:

High habitual caffeine consumers reported greater trait motor impulsivity, that is, acting before carefully deliberating, compared with low habitual consumers. Acute caffeine intake enhanced nonaggressive responding to monetary rewards. However, acute caffeine intake did not influence response inhibition or impulsive, risky, or aggressive behavior in high or low habitual caffeine consumers.

Conclusions:

Thus, while habitual caffeine consumption was associated with greater impulsive behavior, acute caffeine consumption showed no evidence of influencing impulsivity, risk-taking, or aggression.