Caffeine's neural effects

Caffeine is one of the most extensively consumed stimulants in the world. (3) However, compared to short-term effects of caffeine, the long-term effects of caffeine consumption on learning and memory are poorly characterized. Several studies have shown the positive and negative effects of caffeine use. One study found that long-term consumption of low dose caffeine (0.3 g/L) slowed hippocampus-dependent learning and impaired long-term memory (1). The study concluded that long-term consumption of caffeine could inhibit hippocampus-dependent learning and memory partially through inhibition of hippocampal neurogenesis. On the other side of the coin a study done with US navy seals showed that in the most adverse circumstances, moderate doses of caffeine can improve cognitive function, including vigilance, learning, memory, and mood state. The study stated that at doses of 200 mg administration of caffeine may provide a significant advantage (2).

If you look at the science behind caffeine use you will find that Caffeine promotes wakefulness by opposing all of the actions of adenosine, by blocking the adenosine receptors (4). Adenosine acts as a neurotransmitter in the brain (technically a neuromodulator) (5) , the caffeine molecule is similar enough to adenine to fit into adenosine receptors, but is not similar enough to stimulate those receptors. So the main action of caffeine is to block adenosine receptors. What interested me the most was how caffeine affected the adenosine receptors; I believe I could write all day on just this subject, but I will stick to the question at hand. I would like to note that adenosine stimulates and caffeine blocks all classes of adenosine receptors non-selectively (6). The general effect of adenosine in the brain is to inhibit neural activity, and the general effect of caffeine is to increase neural activity. If you think about it, a general increase in neural activity is not always a good thing, in a worst case scenario, general stimulation may result in an epileptic spasm, rather than the controlled activity of thought & learning. Neurons need to rest to work effectively. Caffeine disrupts the time neurons work and rest. This is something I would enjoy learning/discussing more, if anyone has thoughts on the subject?

On another note regarding performance enhancement, there was a study done in regards to the effect of caffeine and aspirin done on college aged men that indicated ingesting caffeine before light exercise significantly increase the leg extension and arm curls exercises. However, the current evidence showed that these benefits are limited to a large relative dose of a caffeine supplement, and at this large dose of caffeine they did have some overall unfavorable effects such as increased stomach distress and increased tremors.

In the non athletic population there have been studies done in regards to caffeine use, as stated earlier caffeine can disrupt neural receptors as well as increased stomach distress and increased tremors. Several studies done on the effect of caffeine as a diuretic, of the studies I have found, there would appear to be no situations where fluid balance might be compromised with caffeine consumption (8,9). Caffeine consumption also appears to be a slight risk factor for chronic daily headaches (10).




1. Myoung-Eun Han, Kyu-Hyun Park, Sun-Yong Baek, et al. Inhibitory effects of caffeine on hippocampal neurogenesis and function. Biochemical and Biophysical Research Communications Volume 356, Issue 4, 18 May 2007, Pages 976-980
2. Harris R. Lieberman, William J. Tharion, Barbara Shukitt-Hale, et al. Effects of caffeine, sleep loss, and stress on cognitive performance and mood during U.S. Navy SEAL training. Psychopharmacology. (2002) 164:250-261
3. Kenneth S. Kendler, M.D., and Carol A. Prescott, Ph.D. Caffeine Intake, Tolerance, and Withdrawal in Women: A Population-Based Twin Study. Am J Psychiatry 156:223-228, February 1999.
4. Nehlig A, Boyet S: Dose-response study of caffeine effects on cerebral functional activity with a specific focus on dependence. Brain Res 2000, 858:71-77
5. R. A. Cunha. Adenosine as a neuromodulator and as a homeostatic regulator in the nervous system: different roles, different sources and different receptors. Neurochemistry International Volume 38, Issue 2, February 2001, Pages 107-125
6. L. V. Lopes, R. A. Cunha, B. Kull, et al. Adenosine A2A receptor facilitation of hippocampal synaptic transmission is dependent on tonic A1 receptor inhibition. Neuroscience
Volume 112, Issue 2, 18 June 2002, Pages 319-329
7. Hudson, Geoffrey M., Matt J. Green, Phillip A. Bishop, and Mark T. Richardson. "Effects of Caffeine and Aspirin on Light Resistance Training Performance, Perceived Exertion, and Pain Perception." Journal of Strength and Conditioning Research 22 (6) (2008): 1950-1957
8. Maughan, R. J., Griffin, J. Caffeine ingestion and fluid balance: a review. Journal of Human Nutrition & Dietetics. (2008) 16(6):411-420.
9. SARAH M. CREIGHTON, S. L. STANTON. Caffeine: Does it affect your Bladder? British Journal of Urology (2008) Volume 66 Issue 6, Pages 613 – 614
10. Ann I. Scher, PhD, Walter F. Stewart, PhD and Richard B. Lipton, M.D. Caffeine as a risk factor for chronic daily headache. NEUROLOGY 2004;63:2022-2027