Coffee consumption and mental performance – Part 2

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Following on from the last post, here is some further information on the topic of coffee and mental performance. This focuses on coffee consumption and memory and dependence.

Caffeine can improve memory
Studies have shown that caffeine intake can improve working memory. Low doses of caffeine can enhance working memory performance, while higher doses have been found to decrease it, possibly due to over-stimulation.

In particular, caffeine improves performance in both low difficulty and low-load memory tasks. In contrast, because high-load and complicated tasks increase arousal, caffeine intake is likely to lead to over-arousal, suggesting that caffeine is particularly effective at improving memory under conditions such as tedious, repetitive or dull tasks.

Caffeine’s effects on memory may also be linked to personality type. The memory of extroverts has been shown to improve with caffeine consumption, whereas there appears to be no difference in working memory with caffeine consumption in introverts.

Effect of caffeine heightened with simultaneous glucose intake
When caffeine and glucose are absorbed together, they have synergistic beneficial effects on verbal memory and sustained attention. The combined administration of caffeine and glucose may increase efficiency of the attention system in the brain however further studies are needed to better understand the combined effects of these two substances.

Caffeine improves mood and may reduce the risk of depression
Low to moderate doses of caffeine have been shown to improve ratings of happiness and reduce levels of anxiety. High doses, however, can increase anxiety, nervousness and jitteriness. In addition, the extent to which caffeine improves mood may be dependent on baseline arousal.

Older adults have been found to be more sensitive to the mood-enhancing effects of caffeine and these effects also depend on the time of day.

Mood can also be affected by the expectation of caffeine consumption, with their mood and attention improving with the belief that they have ingested caffeine. Caffeine also appears to be more effective at improving mood in subjects who do not usually consume caffeine.

Caffeine is not a drug of dependence
The issue of the possibility of dependence on caffeine has been debated for many years. It is possible that maintenance of coffee consumption is caused by the recognition that it is a behavioural stimulant, and not because of any addictive characteristics of caffeine. In addition, the possible reinforcing effects of coffee may not be due to the caffeine, but potentially due to the pleasurable aroma and taste of coffee, as well as the social surroundings that usually accompany coffee consumption.

Drugs such as cocaine, morphine and nicotine trigger a dopamine-related brain circuit involved in dependence and reward, even at low doses, making them ‘addictive’. Studies of rats given caffeine in human doses have failed to find any boost in energy metabolism or dopamine release in this circuit.

Further research in humans has failed to find any activation of the brain circuit of dependence with caffeine intake. This ‘brain mapping’ approach to the study of dependence in humans shows that caffeine does not complete the criteria required to be described as a drug of dependence.

In 1994, the World Health Organization also stated that “there is no evidence whatsoever that caffeine use has even remotely comparable physical and social consequences which are associated with serious drugs of abuse”.

Withdrawal symptoms
Another characteristic linked with drug dependence is withdrawal. Some coffee/caffeine consumers may suffer withdrawal symptoms when they stop drinking coffee. These can include headaches, reduced alertness and drowsiness. These symptoms generally peak 20-48 hours after consumption, and can be avoided if caffeine intake is reduced incrementally.

Consumption of coffee after a phase of abstinence has been found to have a greater effect on mood and choice reaction time. Some studies have reported that this may be due to an increase in cerebral blood flow with caffeine abstinence. However, in some areas related to attention and memory, abstinence from caffeine before the study period does not affect caffeine’s positive effect during the experiment i.e. there is no evidence of withdrawal.

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