Behavioral Effects

Caffeine has several effects on mood and anxiety that depend on the dosage being consumed. Interestingly, caffeine acts as a central and peripheral nervous system stimulant in animals (yes, that includes humans). This could be because of enhanced memory consolidation; but, how much should you drink? Even though this is determined by a number of factors, like genetic polymorphisms that deal with the enzymatic breakdown of caffeine or adenosine, a general list has been developed by various researchers dealing with caffeine’s' side effects. (Temple, 2009)

It is known that low doses are known to influence positively on mood; subjects that had 20 to 200 mg of caffeine reported feeling energetic, efficient and able to concentrate more during a task. This has to do with the stimulation of the locus coeruleus and the serotoninergic median and dorsal raphe nuclei involved in regulation of wakefulness, mood and well being. Caffeine releases serotonin in limbic areas and dopamine in the cortex which is a similar effect that antidepressants have on the human body. (Temple, 2009)

Moderate doses of caffeine, raging from 200mg to 350mg decrease heart rate and increases blood pressure. Moderate doses are associated with enhanced cognitive performance, auditory vigilance, and reaction time. (Brunya, 2010)

High doses of caffeine or low doses on people who have not usually consume as much caffeine may have a more adverse effect, subjects that administered 400 mg of caffeine had feelings of anxiety, nausea, jitteriness, and nervousness.  People who do not consume caffeine regularly are more sensitive to caffeine's anxiogenic and psycho stimulant effects. It is also not recommended for people with naturally anxious individuals or those that suffer from panic attacks. This is a result of the increase in functional activity in the amygdala, a structure in the brain that deals with fear and anxiety. (Brunya, 2010)

Figure extracted from "Acute caffenine consumption enhances the executive control of visual attention in habitual consumers" by Tad T. Brunyé; this shows a graph that shows varius adiminstrations of caffeine on the ANT (attention network based on alerting, orienting, and excecutive control) performace test which sought to numerically measure the "alerting" which maintains vigilance and alertness during the performance of a continuous task. "Orienting" defers to allow individuals to use cues to selectively orient attention to particular regions of space, and "executive control" implies individuals to reduce performace degradation with visual-incompatible information.