Key points
- Caffeine can increase the risk of anxiety and panic attacks
- Excessive caffeine consumption reduces the length and quality of sleep
- Caffeine can be associated with mental health challenges in some people
- Large doses of caffeine can cause bruxism (teeth-grinding at night)
Coffee is universally consumed and is the most popular beverage in the world, although in New Zealand, like the United Kingdom and Australia, many people drink tea as their hot beverage of choice. Coffee has a range of positive health associations; however, many people are sensitive to caffeine or to several of the chemicals naturally present on the coffee bean. So, while coffee might be a generally health-promoting drink, it isn’t the right choice for everyone. Genetic polymorphisms are responsible for differing metabolism and clearance rates of caffeine, and they are also related to the anxiety-inducing effects of caffeine that some people experience.3
Caffeine use disorder
Caffeine use disorder is recognised by the World Health Organisation and many healthcare professionals. Experiments show that caffeine exhibits behavioural and psychological effects similar to other drugs of dependence.4
Panic attacks
Around 50% of people with panic disorder experience panic attacks after consuming caffeine.1
Sleep
Caffeine reduces total sleep time and adversely affects sleep quality.2 Caffeine also typically prolongs the time taken to get to sleep, increases waking and arousal during the night, and reduces slow-wave sleep. Individual responses vary though and negative effects are increased with dose and proximity to sleep-time.8
Caffeine reduces total sleep time and adversely affects sleep quality
Caffeine use and seizures
Caffeine is an adenosine antagonist, meaning that it effectively ‘blocks’ the action of the relaxing neurotransmitter adenosine. Adenosine is implicated in reducing seizures and caffeine conversely might encourage seizures, especially with high doses and acute use. However, long-term habitual use may protect against seizures.5 Caffeine also increases ketone body concentrations and this might also provide an anti-seizure effect.
Caffeine and psychological disorders
Case evidence has linked caffeine to psychiatric problems and mood disorders,6 however, around 1-2 cups of tea or coffee per day is associated with reduced rates of depression.7
Around 1-2 cups of tea or coffee per day is associated with reduced rates of depression
Caffeine and fertility
Semen quality does not appear to be affected by caffeine from cocoa, tea, and coffee drinks but there is a reduction in semen volume, count, and concentration with caffeine-containing soft drinks. There may also be some DNA damage resulting from caffeine but population data doesn’t suggest that caffeine is a likely contributor to male infertility.9 The negative effect on semen quality from soft drinks is likely to come from the sugar content or increased overall energy intake rather than caffeine.
Teeth-grinding
The odds of experiencing sleep bruxism (teeth grinding at night) is around 50% higher for people drinking 8 or more cups of coffee per day.10
Caffeine and liver disease
Caffeine had been linked to reduced rates of non-alcoholic fatty liver disease because of regular caffeine-consumption in the form of coffee results in reduced risk of liver fibrosis and inflammation.11 However, reviews of the literature have shown that caffeine itself is not associated with reduced prevalence of this disorder.12 This supports the theory that some of the health benefits (and indeed some of the triggers for people sensitive to coffee) are not purely related to caffeine but also to the myriad phytochemicals in the coffee bean.
Caffeine and blood pressure
The effects of caffeine on blood pressure are unclear. While it is generally considered to increase blood pressure, results of studies vary considerably, and age, sex, ethnicity, gender, and individual differences in tolerance to caffeine and its metabolism play a role in the effects on blood pressure and other health outcomes.13
Tolerance to caffeine and its metabolism play a role in the effects on blood pressure and other health outcomes
Caffeine and diabetes risk
It has been posited that caffeine might be a risk factor for diabetes. While 400-500 mg of caffeine has been demonstrated to increase blood glucose concentration (post-ingestion) by around 22% and insulin by around 33% (while also transiently reducing insulin sensitivity1),2 for a short time after consuming, it is unlikely to be a causative factor for diabetes as systematic reviews consistently show a correlation between coffee intake (containing caffeine) and a reduced risk of diabetes.3-6
Systematic reviews consistently show a correlation between coffee intake (containing caffeine) and a reduced risk of diabetes
References
1. Buhiji AM. The Impact of Caffeine in Triggering Panic Attacks among Adults with Panic Disorder: A Systematic Review and Meta-analysis of Randomized Controlled Trials. Canadian Journal of Clinical Nutrition. 2020.
2. Bonnar D, Gradisar M. Caffeine and Sleep in Adolescents: A Systematic Review. Journal of Caffeine Research. 2015;5(3):105-14.
3. Fulton JL, Dinas PC, Carrillo AE, Edsall JR, Ryan EJ, Ryan EJ. Impact of Genetic Variability on Physiological Responses to Caffeine in Humans: A Systematic Review. Nutrients. 2018;10(10):1373.
4. Caffeine Use Disorder: A Comprehensive Review and Research Agenda. Journal of Caffeine Research. 2013;3(3):114-30.
5. van Koert RR, Bauer PR, Schuitema I, Sander JW, Visser GH. Caffeine and seizures: A systematic review and quantitative analysis. Epilepsy & Behavior. 2018;80:37-47.
6. Wang HR, Woo YS, Bahk W-M. Caffeine-induced psychiatric manifestations: a review. International Clinical Psychopharmacology. 2015;30(4):179-82.
7. Grosso G, Micek A, Castellano S, Pajak A, Galvano F. Coffee, tea, caffeine and risk of depression: A systematic review and dose–response meta-analysis of observational studies. Molecular Nutrition & Food Research. 2016;60(1):223-34.
8. Clark I, Landolt HP. Coffee, caffeine, and sleep: A systematic review of epidemiological studies and randomized controlled trials. Sleep Medicine Reviews. 2017;31:70-8.
9. Ricci E, Viganò P, Cipriani S, Somigliana E, Chiaffarino F, Bulfoni A, et al. Coffee and caffeine intake and male infertility: a systematic review. Nutrition Journal. 2017;16(1):37.
10. Bertazzo-Silveira E, Kruger CM, Porto De Toledo I, Porporatti AL, Dick B, Flores-Mir C, et al. Association between sleep bruxism and alcohol, caffeine, tobacco, and drug abuse: A systematic review. The Journal of the American Dental Association. 2016;147(11):859-66.e4.
11. Wijarnpreecha K, Thongprayoon C, Ungprasert P. Impact of caffeine in hepatitis C virus infection: a systematic review and meta-analysis. European Journal of Gastroenterology & Hepatology. 2017;29(1):17-22.
12. Shen H, Lipka S, Shahzad G, Kumar A, Mustacchia P. Association Between Caffeine Consumption and Nonalcoholic Fatty Liver Disease: A Systemic Review and Meta-Analysis: 537. Official journal of the American College of Gastroenterology | ACG. 2014;109:S158.
13. De Giuseppe R, Di Napoli I, Granata F, Mottolese A, Cena H. Caffeine and blood pressure: a critical review perspective. Nutrition research reviews. 2019;32(2):169-75.
14. Caffeine as Treatment for Alzheimer’s Disease: A Review. Journal of Caffeine Research. 2015;5(2):61-4.
1. Shi X, Xue W, Liang S, Zhao J, Zhang X. Acute caffeine ingestion reduces insulin sensitivity in healthy subjects: a systematic review and meta-analysis. Nutrition Journal. 2016;15(1):103.
