Studies examining the effects of energy drinks have highly variable study designs, and long-term randomized controlled trials are lacking.[1] Consequently, further high-quality studies are needed to fully understand the short- and long-term drawbacks of energy drinks and shots. That said, several papers reviewing the evidence from observational studies have highlighted public health concerns about energy drinks, which are due to their numerous side effects and their potential adverse health effects.[2][3][4][5]
Common side effects of energy drinks include headache, shortness of breath, jitteriness/restlessness, gastrointestinal upset, and sleep problems (e.g., insomnia).[6][7][8][8] Furthermore, observational studies indicate that frequent energy drink consumers are more likely to consume other caffeine-containing beverages,[9] and are also more likely to engage in unhealthy behaviors, such as alcohol, drug use, and smoking, and more likely to make less-healthful dietary choices such as sugar-sweetened beverages and junk foods.[9][10][11][12][13][14]
Consumption of energy drinks and shots is also associated with increased stress, anxiety, and depression-related symptoms.[15][16][8] However, such health risks are often derived from observational studies involving cross-sectional study designs and correlation analyses, which makes it difficult to be confident about causality. Furthermore, “reverse causation” is also possible — i.e., people with conditions like anxiety or depression might be more likely to consume energy drinks to cope with symptoms. That said, one 2-year observational study found that male participants who went from being a non-energy drink user to an energy drink user had an increase in stress, anxiety, and depression-related symptoms over the course of the study, even after controlling for known confounders.[17] Further studies are needed to make firm conclusions concerning the association between energy drink use and mental health.
Consuming an energy drink can acutely raise heart rate and blood pressure at rest[18][19][20] and during exercise,[21][18] and delay their recovery following exercise.[21][18] Energy drinks can also disturb electrical activity in the heart: electrocardiogram (ECG) readings show a prolonged QRS complex (the time it takes for heart muscles to contract) and lengthened QTc intervals (the time it takes for heart muscles to relax after they start to contract).[18] The long-term effects of such outcomes are currently unclear, but people with heart conditions should exercise caution when consuming energy drinks and consult their doctor if they are unsure.
There have been several case reports of adverse cardiovascular events occurring following the consumption of energy drinks and shots.[22][23][24][25][26][27][28] However, these have largely occurred when energy drinks or shots were consumed either in excess or in combination with other substances with potential adverse effects, such as alcohol and drugs.[29] While the population-level incidence of an adverse event is low[30], it’s important to note that, particularly for members of certain groups (children, teenagers, people with underlying heart conditions), dramatically exceeding one's recommended daily caffeine intake limit, whether by energy drinks alone or in combination with other caffeine-containing food and drink, carries risks to one's health.[31][32]