However, in scientific terms, mood and emotion have different definitions. A mood is a relatively long-lasting affective state51; while an emotion is of shorter duration. It has been suggested that emotions can be defined by episodes of synchronised change, with components such as bodily reactions (such as blushing), and motor expressions52.
In Europe, mental health and mental disorders (including depression and anxiety) pose a significant public health challenge53. Every year, 1 out of 15 people suffer from major depression in Europe, and if anxiety and all forms of depression are included, nearly 4 out of 15 people are affected54.
Research suggests that diet and exercise can affect neuronal development and physiology and protect the brain from neurological illnesses or injuries55. Of note, coffee, cocoa and tea are being actively investigated because they contain polyphenolic compounds that may have beneficial effects on mental health, including behaviour, mood, depression and cognition56.
Caffeine and mood
A review by A. Nehlig suggests that repeated administration of 75mg of caffeine (the equivalent of one cup of coffee) every 4 hours can result in a pattern of sustained improvement of mood over the day: however high intakes may be associated with an increase in tense arousal including anxiety, nervousness and jitteriness (i.e. feeling shaky or uneasy)26. A dose-related improvement in subjective measures of calmness and interest were found after consuming caffeine, suggesting that mood improvement may depend on baseline arousal26. Highly-fatigued subjects may be more likely to experience larger subjective mood changes than non- or moderately-fatigued subjects26.
Studies have reviewed the impact of other intakes of caffeine: in one such study, a single 60mg caffeine dose elicited a clear enhancement of sustained attention and alertness, contentment and mood27. A further study concluded that an intake of 100mg caffeine significantly decreased lethargy/fatigue and increased vigor28. The European Food Safety Authority (EFSA) concluded that a cause and effect relationship between improved alertness and attention and 75mg caffeine (approximately the amount in a regular cup of coffee) had been established1.
Older adults seem to be more sensitive to the mood-enhancing effects of caffeine than younger individuals29. Mood effects are also influenced by the time of consumption, with the most prominent effects showing in the late morning29. In fact, one study has suggested that caffeine could potentially be used as a nutrition supplement for older adults, enhancing mood and improving cognitive performance in their daily living tasks57. However, further research is needed before any firm conclusions can be drawn.
Research also suggests that caffeine tends to have a more beneficial effect on habitual consumers’ moods (compared to non-consumers), but there are greater improvements in performance when drunk by non-consumers58. It also seems that mood is not only modulated by caffeine itself but also by the expectation of having consumed caffeine, which improves mood together with attention10.
The effect of caffeine in stimulating self-reported alertness and mood was not thought to persist for extended periods of time, with the effects peaking during the first 4 hours after ingestion. Research in office workers suggests that consuming caffeine with ornithine (an amino acid involved in protein metabolism, found in foods such as dairy products and meat, and which can be synthesized in the body) in the morning had a positive effect on self-reported mood (especially reducing “feelings of fatigue”, and increasing “willingness to work”, and “vigor”) in the late afternoon, suggesting that ornithine potentiated the physiological action of caffeine59.
References for graphic:
- Improves alertness1.
- May improve working memory26.
- Different effects different people37,74-76.
Extensive research on caffeine intake has been associated with a range of reversible physiological effects at both lower and higher levels of intake, suggesting that caffeine intake has no significant or lasting effect on physiological health60.
Caffeine, carbohydrates and mood
Consuming nutrients and biologically-active compounds together is of interest to researchers, as it gives a greater understanding of the impact of food and drink in the body. The combination of caffeine and carbohydrates has been of particular interest61,62.
Administered in common beverages with appropriate placebo controls, one study reviewed the impact of coffee and glucose on mood and performance both separately and together, and concluded that neither glucose nor caffeine showed a significant effect on cognitive performance. This was surprising in the case of caffeine, as multiple studies suggest it improves cognitive performance (as referenced in the prior ‘Caffeine and Mental Alertness’ subtopic). The authors acknowledged that significant confounding factors may have interfered with the results, and that caffeine did result in increased perceived preserved mental energy under test conditions, although further work to consider whether these mood changes would also result in increased motivation during a challenging task, would be advisable61.
Further research combining a moderate dose of caffeine (200mg) together with a low carbohydrate intake (50g white bread) positively influenced mood and cognitive performance, while carbohydrate intake alone did not62. In this research, the key element leading to improved mood and mental performance was the presence of caffeine.
A small pilot study reported that caffeinated coffee had a more robust positive effect on high-level mood and attention processes than decaffeinated coffee. Interestingly, the authors found that decaffeinated coffee could also improve mood and performance. This suggests that substances other than caffeine, such as chlorogenic acids, may also affect mood and performance63. However, this effect needs to be confirmed in a larger group of individuals.
Caffeine and effect on depression
Research suggests that caffeine may help to relieve depressive symptoms or help to protect against depression. A 2016 meta-analysis accounting for a total of 346,913 individuals and 8,146 cases of depression suggested that coffee consumption may have a protective effect. A dose-response analysis suggests a J-shaped curve, with the effect reported for up to approximately 300mg caffeine (approximately 4 cups of coffee) per day30.
A number of specific studies have investigated caffeine consumption in relation to the risk of depression:
- A study of 50,739 women (average age 63 years), part of the Nurses’ Health Study, suggested that women who consumed 2-3 or at least 4 cups of caffeinated coffee per day were, respectively, 15% or 20% less likely to develop depression, compared to those who drank at most one cup of caffeinated coffee per week. The consumption of decaffeinated coffee had no impact on depression risk. This observational study suggests the possibility of a protective effect of caffeine on depression risk31.
- A cohort study of Finnish men reported a 77% risk reduction for depression in heavy coffee drinkers (those who consumed over 813mg caffeine daily). This effect was limited to coffee and was not found with either tea or caffeine alone32.
- A Japanese cross-sectional study reviewed the impact of consumption of both green tea and coffee on depressive symptoms, suggesting that both green tea (more than 4 cups per day) and coffee (more than 2 cups per day) may offer protection against depression33.
- A cross-sectional study in 10,177 Korean individuals aged 20-97 years, who participated in the fifth Korean National Health and Nutrition Examination Survey, suggested that coffee consumption may have a small protective effect on the risk of depression34.
Research on depressive symptoms in participants who received either caffeinated coffee (150mg caffeine), or decaffeinated coffee (9mg caffeine) showed that caffeinated coffee increased co-operative game behaviour and sadness communication, suggesting that caffeinated coffee may improve social support and relieve depressive symptoms64.
Finally, coffee and caffeine consumption might be favoured by some specific patient groups, including patients with bipolar disorders, who were reported to consume more social drugs such as tobacco and coffee than the general population65, and schizophrenic patients66. It has been hypothesized that patients smoke and drink coffee to reduce medication side effects such as anhedonia (inability to feel pleasure), or to improve cognitive symptoms linked to the treatment.
Caffeine and emotion
Caffeine reliably increases arousal1, but it is currently unclear if and how it influences other dimensions of emotion such as positive versus negative feelings.
One study evaluated emotional responses to coffee beverages to develop a lexicon to describe the feelings that occur during coffee drinking. The results suggested that coffee drinkers sought different emotional experiences from their drink: some preferred coffee to elicit positive-lower energy feelings, some liked to be aroused by the positive-high energy emotions, whilst others desired feelings of a focused mental state67.
Research has suggested that caffeine may accentuate non-habitual caffeine consumers’ emotional responses to negative situations, but not how they choose to regulate such responses68. Further research has considered the impact of caffeine consumption in situations where emotions were already stimulated by watching negative film clips, concluding that caffeine consumption may produce increases in self-reported measures of tension, anxiety and anger. This effect was altered when coffee was consumed with theanine (found in tea), which decreased this effect of caffeine69.
Dopamine is a neurotransmitter that helps to control the brain’s reward and pleasure centres. It also helps to regulate emotional responses.
Research has suggested that dopamine may mediate some of the behavioural effects of caffeine. After drinking a cup of coffee, caffeine is absorbed into the blood stream and transported around the body to the brain. In the brain, adenosine acts as a central nervous system depressant and promotes feelings of tiredness. Due to its similar structure, caffeine may bind to the adenosine receptors, acting as an imposter and blocking the actions of adenosine, leading to feelings of alertness70. For further explanation, watch this video on coffee and its effect on the brain.
Research suggests that caffeine consumption may be associated with an increase in the availability of dopamine receptors in the brain, suggesting that caffeine may enhance arousal in part by up-regulating dopamine receptors71.