What caffeine does to your body and brain

Many of us can't start our day without a jolt of caffeine.

Various caffeinated drinks affect your health in different ways — a new study shows coffee seems to be associated with longer life, while many energy drinks have surprisingly high sugar levels.

Caffeine itself is a stimulant with some positive and negative effects. It makes most of us feel more alert, awake, and focused, but too much can also backfire.

It also affects a host of processes in our bodies, including our digestion, metabolism, and vision. 

Here's what's really going on after you drink a cup of joe.

SEE ALSO: Drinking more coffee is associated with a longer life, according to new research

Caffeine is the most commonly used psychoactive drug in the world.

One of the things rarely mentioned about caffeine is that it is, in fact, a drug. In fact, it’s the most commonly used psychoactive drug in the world, which is probably why we don’t think about it as a drug.

Caffeine has psychoactive effects, and changes the way we feel and interact with the world around us. Yet think of how many of us can’t — or won’t — go through a day without it.

Harvard neuroscientist Charles Czeisler has hypothesized that caffeine, combined with electricity, allowed humans to escape natural patterns of sleep and wakefulness, breaking them free from the cycle of the sun. That change, he wrote in National Geographic, enabled the “great transformation of human economic endeavor from the farm to the factory.”

It makes us feel alert, at least for a while.

It’s normal to grow tired as the day progresses — our brains naturally producemore of a molecule called adenosine from the time we wake up until the time we go to sleep. Scientists think this helps us get to bed at night.

Caffeine hijacks this natural process by mimicking adenosine in the brain. It latches onto the receptors designed for adenosine, pushing them out of the way. As a result, we’re left feeling more alert and awake.

Eventually, however, adenosine wises up to caffeine’s act and makes new receptors for the sleep-inducing molecule to start latching onto again.

This is why your morning cup of coffee can suddenly turn into two — the more receptors you have, the more caffeine you need to plug them up.

It boosts our mood.

As a central nervous system stimulant, caffeine doesn’t just boost alertness, it can also improve your mood.

This is due to the same adenosine-blocking effect that makes you feel alert. By blocking adenosine’s relaxing effects, caffeine lets dopamine and glutamine (other natural stimulants produced by your brain) run wild, making you more alert, less bored, and providing a mood boost.

Interestingly, a number of studies have found a connection between caffeine consumption and a reduced risk of depression— especially when it's consumed in the form of coffee. Research has even suggested caffeine lowers the risk of suicide, at least for men. However, at least one of these studies only found this connection with caffeinated coffee, not tea, though others found the same effect for tea as well.