Too Much Coffee? How Caffeine Affects Your Brain

Almost everyone loves to have a nice, hot cup of coffee every once in a while. In fact, studies show that 85% of the U.S. population consumes caffeine every single day, whether it be with coffee or soda. With all of the caffeine consumed by most Americans constantly, have you ever wondered how caffeine affects your brain? Why do you feel so awake and full of energy after you get some caffeine? And after taking in caffeine every single day, why do you feel like it’s not working? Why do some people have to drink three or more cups of coffee a day to feel awake while others only need a few sips? Read below to find out how caffeine affects your brain!

How caffeine affects your brain

How caffeine affects your brain

Where is Caffeine Found?

Caffeine occurs naturally in the leaves, seeds, or fruits of more than 60 plants, including coffee beans, tea leaves, cacao beans, kola nuts, and more. This stimulant is found common beverages and foods including:

  • Brewed and instant coffee
  • Caffeinated, brewed tea
  • Caffeine-containing cola and other soft drinks (namely, Coke-a-Cola and Pepsi)
  • Cocoa
  • Chocolate
  • Chocolate milk

How Caffeine Affects Your Brain: What Happens “Inside” When You Drink Coffee?

No matter how you get your caffeine, it changes the way the body and the brain work. Once consumed, caffeine is absorbed into the bloodstream and body tissues within 45 minutes. Caffeine reaches its peak level in the blood within 1 hour and remains there for 4-6 hours.

Caffeine belongs to a group of drugs called Central Nervous System (CNS) stimulants. When caffeine hits the brain, it suppresses a type of neurotransmitter called adenosine. Adenosine works to influence attention, alertness, and sleep. It builds up in your brain as the day goes on, and when it reaches a certain level, your body decides that it’s bedtime. This is usually why at the end of the day, when it gets late and dark outside, you have trouble staying awake and paying attention. While you sleep, adenosine resets back to zero, and you wake up in the morning alert and ready to function.

What caffeine does is compete with adenosine. If you think on the protein-enzyme level, caffeine has is shaped similarly to adenosine, so it binds to certain receptors in the brain like a key fits into a lock. If caffeine reaches the lock first, then adenosine cannot bind to make you feel sleepy. By blocking adenosine, caffeine keeps your brain’s neurons running adeptly, so that you feel awake when you really should be feeling sleepy.

While this process of caffeine blocking adenosine is going on, stimulating brain neuro-hormones like dopamine and glutamate are able to flow more freely, without much restriction. They work to give your body a surge of energy, improve mental performance, and slow down age-related mental decline. Along with those two chemicals, caffeine also increases the amount of serotonin that’s in your brain. Serotonin influences your major mood swings, so a large surge in the chemical will make you feel more positive and less depressed.

Brain Benefits of Caffeine

1. Alertness

The European Food Safety Authority (EFSA) concluded that there is a link between consuming at least 75 milligrams of caffeine and increased attention and alertness. They suggest that taking in 160-600 milligrams of caffeine can improve mental alertness, reasoning, speed, and memory when subjects feel fatigued and sleepy.

2. Overall Brain Functioning

Mentioned above is a description of how caffeine works at adenosine receptors in the brain. Along with that, caffeine has specific compounds inside, like polyphenol antioxidants, that act on various pathways in the brain and may play a protective role of proper brain functioning

How caffeine affects your brain

How caffeine affects your brain

3. Prevents Cognitive Decline

Studies suggest that a regular, moderate consumption of caffeine may slow down physiological, age-related cognitive decline, especially in women and those who are over 80 years old. It therefore can also decrease the risk of cognitive decline in diseases like Alzheimer’s or Parkinson’s.

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4. Memory

Research from Johns Hopkins University suggest that a small dose of caffeine after a learning session may help to boost long-term memory.

Other Effects of Caffeine

Since caffeine blocks adenosine, there is an increase in excitatory neurotransmitters in the brain. Dopamine was already mentioned above, but caffeine also stimulates the release of epinephrine from your adrenal glands. Epinephrine is usually associated with your fight-or-flight response, but it overall makes the body feel extremely surged with energy. However, although caffeine’s main effect is to produce a temporary sense of alertness, it can cause other issues, such as:

  • Disrupted sleep
  • Fast or uneven heartbeat
  • Jitters and shaking
  • Hypertension (high blood pressure)
  • Headaches
  • Nervousness
  • Dizziness
  • Dependency
  • Dehydration

Interesting Genes Associated with Coffee

Do you have that one friend who can drink a large, jumbo Cafe Espresso and then feel sleepy soon after, but if you do the same, you’ll stay up for hours? According to researchers, caffeine sensitivity may be due to genetics. The effects of coffee vary from person to person because one of the main enzymes found in your liver, CYP1A2, is responsible for metabolizing coffee. How much CYP1A2 you create depends on your individual CYP1A2 gene. The productivity of this gene is different for everyone, which is why some people can metabolize coffee better than others.

Even more interesting genetics at play have been researched by the Harvard School of Public Health. In a study of 120,000 people, they found six new genetic variants associated with the way people metabolize caffeine:

  • There are 2 genes specifically related to coffee metabolism. Those people who drink more coffee on average are likely to have unusual forms of these genes.
  • There are 2 genes associated with how caffeine affects your brain with positive reinforcement. Heavy coffee drinkers are more likely to have variants of these genes that lead to increased levels of serotonin in the brain as a response to caffeine. That means that these people feel especially happy, rewarded, and content when they consume caffeine.
  • The other 2 genes regulate fat and sugar in the bloodstream as a response to caffeine. These genes were not previously linked to caffeine’s neurological effects but the new research shows somewhat of a correlation. People who drink more coffee often have a mutation that influences glucose sensing in the brain.

Overall, the Harvard study showed that no two coffee drinkers are alike. For everyone, their genetic combinations and brain chemistry vary and are dependent on how much caffeine they consume over time.

Other studies show that caffeine can improve your learning by up to 10%. It can even relieve headaches and migraines by constricting blood vessels in the brain that are opening too wide.

Is Caffeine Addictive?

How caffeine affects your brain

How caffeine affects your brain

Although there has been much debate on whether or not caffeine is an addictive substance, in 2013, the American Psychiatric Association considered it to be so. They added “Caffeine Withdrawal” to the list of recognized conditions in the DSM-V (Diagnostic and Statistical Manual of Mental Disorders). However, not all caffeine consumers suffer from withdrawal symptoms once they stop consumption.

Symptoms of caffeine withdrawal begin about 12-24 hours after a sudden stop in caffeine intake and they reach a peak after about 20-48 hours. These symptoms include headaches, sleepiness, irritability, lethargy, constipation, insomnia, flu-like symptoms, and more. Gradually reducing consumption over a period of days will help prevent these symptoms.

However, research has shown that caffeine does not activate the pathways in the brain that are related to addiction and reward in opposition to other drugs. Therefore, the debate still exists of coffee being addictive because many scholars have concluded that it is not.


For more information about the effects of caffeine on your brain and overall health, check out:

Sources: 1, 2, 3