It's in coffee, tea, soda and energy drinks. There's even a bit of it in chocolate. In fact, caffeine is one of the most widely-consumed substances in the world, and there are many people who say they can't start their day without it.
"It makes us feel better, particularly if we haven't slept well or we've been working late at night," noted neurologist Nora Volkow, director of the National Institute on Drug Abuse, adding "we really don't completely understand why."
So she and her colleagues at Brookhaven National Laboratory in Upton, New York, decided to get to the bottom of this phenomenon and their work reveals how caffeine changes our brains to give us that buzz.
Inside a brain on caffeine
The researchers brought volunteers into the lab and had them swallow caffeine tablets — the equivalent of drinking 2 or 3 cups of strong coffee — then put them into a PET scanner and observed subsequent brain activity.
Like other drugs, caffeine boosts the natural activity of a brain chemical called dopamine, which motivates us to seek out the things in life that bring pleasure and happiness.
Drugs such cocaine and amphetamine flood the brain with dopamine, which can lead to addiction. But Volkow found that caffeine works slightly differently. It increases the number of receptors that dopamine molecules can latch onto, which makes us feel perky and alert.
"This was, interestingly, exactly the opposite of what we observed with sleep deprivation," Volkow said, explaining that just one night of sleep deprivation saw the number of dopamine receptors go down. The same thing happens as we start to feel tired late in the day, so caffeine blocks that natural process to can keep us awake.
Is caffeine addictive?
But if caffeine is changing our brains and affecting the same molecule as cocaine, is it addictive?
According to Volkow, no. "The reality is that caffeine does not produce these compulsive patterns that you see with other drugs [that lead to] catastrophic consequences, so, in that respect, caffeine is not addictive in the same sense."
While caffeine does just enough to keep us zipping along without taking us over the edge, it is possible to have too much. Laura Juliano, a clinical psychologist at American University, agrees with Volkow's assertion that it's not addictive, but warns that, in excess, caffeine can affect someone's daily functioning and well-being. For these individuals, she says, not drinking caffeine can cause a host of negative symptoms — headaches, nausea, flu-like symptoms, and excessive fatigue.
Indeed, symptoms of caffeine withdrawal are often mistaken for other illnesses. Juliano says that more research is needed so doctors are better prepared to recognize excessive caffeine use and withdrawal as the actual disorder.
In moderation, however, caffeine has been shown to provide a number of short-term and long-term health benefits. Recent research points to moderate caffeine consumption as a likely buffer against cognitive decline and Alzheimer's Disease later in life.
So have another cup of coffee!