Adverse effects of excessive caffeine intake
800 mg/day is well above the maximum recommended amount (1)(3). High doses of caffeine (>600 mg/day) can increase the risk of spontaneous abortion in women (2). Caffeine directly affects the heart. Side effects related to this becomes especially pronounced at higher doses, and can cause tachycardia, and arrythmias (5).
Excessive caffeine consumption can result in severe psychological dependence and withdrawal (5).
Caffeine use is associated with increased risk of developing anxiety disorders (4).
Tolerance also develops with chronic caffeine consumption. Increased doses will be required to achieve the desired effects of enhanced concentration and reduction of fatigue (3).
Moderate amounts (100-200 mg/day) however, have been demonstrated to be safe (3).
Treatment of ADHD with caffeine
There is some evidence to suggest that caffeine is an effective treatment for ADHD (5)(9). However, caffeine is not indicated for ADHD, and tolerance develops rapidly.
A Comparison of Stimulants
The drugs referenced interact with organisms in unique ways (i.e.: possess unique pharmacodynamics), and in turn, differ in their therapeutic effects, and side effects. The drugs also have varying pharmacokinetic profiles, meaning that they are absorbed, distributed, excreted, and metabolized differently in the body.
Caffeine is an antagonist at adenosine receptors 1 and 2A. This means
it binds to said receptors without activating them. The presence of
caffeine at the adenosine receptors prevents adenosine (an inhibitory
neurotransmitter) from binding (and producing a response), thereby
causing stimulation (1) . This activity also induces neurotransmitter
release (2) .
From Mechanism of action (MOA) of Caffeine.
Additionally, caffeine is a more mild CNS stimulant than the amphetamines (i.e.: methylphenidate and amphetamine). The amphetamines are a more effective treatment for ADHD than caffeine (10)
Methylphenidate (Ritalin, Concerta)
Methylphenidate is a reuptake inhibitor of dopamine (DA), and to a lesser but still marked degree, noradrenaline (NE) (6). This activity increases the effect of these neurotransmitters, resulting in a reduction of symptoms.
Amphetamine (Vyvanse, Adderall, Dexedrine)
Amphetamine is a releasing agent of DA, NE, serotonin (5-HT) (6).
Side effects such as anorexia, weight loss, and nausea tend to occur more commonly with amphetamine than methylphenidate. (8)
In regards to the therapeutic effect, there is no significant difference between methylphenidate and amphetamine overall (7).
- Caffeine: How much is too much? http://www.mayoclinic.org/healthy-lifestyle/nutrition-and-healthy-eating/in-depth/caffeine/art-20045678
- Coffee http://lpi.oregonstate.edu/mic/food-beverages/coffee
- Medicines in my Home Caffeine and Your Body https://www.fda.gov/downloads/UCM200805.pdf
- Common Psychiatric Disorders and Caffeine Use, Tolerance,and Withdrawal: An Examination of Shared Genetic and Environmental Effects https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3443633/
- Caffeine Psychological Effects, Use and Abuse http://orthomolecular.org/library/jom/1981/pdf/1981-v10n03-p202.pdf
- Methylphenidate and dexmethylphenidate formulations for children with attention-deficit/hyperactivity disorder.
- Clinical Gains from Including Both Dextroamphetamine and Methylphenidate in Stimulant Trials https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3842881/
- A post hoc comparison of the effects of lisdexamfetamine dimesylate and osmotic-release oral system methylphenidate on symptoms of attention-deficit hyperactivity disorder in children and adolescents. https://www.ncbi.nlm.nih.gov/pubmed/23801529
- Tea consumption maybe an effective active treatment for adult attention deficit hyperactivity disorder (ADHD). https://www.ncbi.nlm.nih.gov/pubmed/21277687
- Caffeine versus methylphenidate and d-amphetamine in minimal brain dysfunction: a double-blind comparison. https://www.ncbi.nlm.nih.gov/pubmed/1096645