Weak signaling of the neurotransmitter dopamine is a main contributor to Attention Deficit Hyperactivity Disorder (ADHD). The two main prescriptions for ADHD, methylphenidate (Ritalin) and amphetamine, both target dopamine (stimulating its release into, and inhibiting its re-uptake from, the synapse). Adenosine is a neurotransmitter that reduces dopamine’s actions, kind of like an unwanted side kick that gets in the way of our hero, dopamine. Caffeine has a similar structure to adenosine, so it binds to adenosine’s receptors in the synapse, keeping adenosine from reducing dopamine’s actions. So caffeine is like a babysitter for adenosine, letting dopamine do its job without constant interference from the side kick. A medical hypothesis, based on observation and theory (not systematic research) was published in 1985* suggesting that caffeine from coffee intake by adults kept many of them from experiencing ADHD, implying that if children with ADHD consumed caffeine before they acquired a taste for coffee in adulthood their symptoms might decrease. Only one systematic study** available on PubMed on this topic has been done do date. It showed that mice with ADHD genetics consuming caffeine significantly increased their spatial learning (escape time from a maze), whereas caffeine had no such effect on normal mice. Between a dose of 1-10 mg caffeine / kg body weight there was no difference in the effect, meaning that only a small amount of caffeine was needed, and any more than that was overkill in terms of caffeine’s effect on adenosine function. For someone weighing 20-100 kg, this corresponds to 20-100 mg of caffeine, less than the amount in a cup of coffee.
Clyde’s Thoughts: Amphetamines and caffeine are both stimulants, in part because of their direct (amphetamines) and indirect (caffeine) impact on dopamine action. Although the research thus far is scarce on this topic, I believe that the medical observations, theory, and limited data combine to make a powerful argument for considering the use of caffeine to reduce ADHD symptoms. Note, however, that caffeine also stimulates adrenaline release, so excess caffeine could easily make one’s condition worse. And since caffeine’s half-life in the body is several hours, it should not be consumed in the second half of one’s day to protect sleep quality.
Clyde’s Advice: A cup of coffee contains 100-150 mg of caffeine, the right amount for an adult, and most sodas contain 30-55 mg caffeine, the right amount for children. However, artificial colors and flavors are the most highly correlated compounds to making ADHD worse. As a result, most sodas contain ingredients that will make ADHD much worse than any potential improvements from caffeine. If soda is important to you or someone you care about, offer them a soda containing only natural ingredients you can easily understand, but these products will not generally contain caffeine. Note that I am not complicating this discussion with the pros and cons of unhealthy sugars in soda. Alternatively, caffeine can be consumed as a 100 mg (for children) or 200 mg (for adults) tablet per day, which is ½ (children) or 1 (adults) NoDoz, Alert, Stay Awake, or Vivarin tablet. Coffee is the main source of antioxidants for adults in the US other than those addicted to chocolate (a sad fact that results from low vegetable consumption), so 1-2 regular cups of coffee or 1 regular espresso is a better alternative than a tablet. Keeping within these amounts will not only minimize the fight-or-flight response that may obscure any benefits, but will also minimize your brain’s adaptation to habitual caffeine intake. Both of these effects would reduce caffeine’s effect over time.
The Bottom Line: Caffeine is worth considering to reduce the symptoms of ADHD, but more than 1 mg caffeine / kg body weight is no more helpful than 10 times that amount. Lower amounts minimize caffeine’s adrenaline and habituation effects, so not only is it true that “less is more”, but that “more is nothing” (meaning that consuming too much will mask any benefits). I suggest no more than the amount of caffeine that is in 1-2 sodas for children (50-100 mg, but in tablet form) or 1-2 cups of coffee for adults (or 1 espresso, 100-200 mg). This is ½ (children) or 1 (adults) caffeine tablet (NoDoz, etc).
*“Will population decreases in caffeine consumption unveil attention deficit disorders in adults?” Dalby JT, Med Hypotheses, 18 1985 163. Research paper quality score: C
**”Caffeine improves spatial learning deficits in an animal model of attention deficit hyperactivity disorder (ADHD)”, Prediger RDS et al., Int J Neuropsychopharmacology 8 2005 583. Research paper quality score: 2