It’s that time of the year when the lineups at Tims, Starbucks, and Second Cup get longer than usual, with students opting for that extra large rather than large cup. Some of us may not even consider themselves coffee drinkers, but that can of Red Bull or Monster becomes so appealing during exam time.

Whether it’s cold or warm, each of those drinks has one key ingredient: caffeine. It stimulates our brain and “wakes” it up, so we can do more tasks throughout the day. That comes with consequences: addiction and desensitization.



Many parts of the brain have receptors with multiple functions. For sleep and alertness, these receptors react to a molecule called adenosine. Throughout the day, we accumulate adenosine, and become more tired. When enough receptors fill up with adenosine, our brain tells us to go to sleep. As we sleep, the adenosine is cleared.

Caffeine shares a similar shape to adenosine, so when we drink that Tim Hortons double double around 6 p.m., caffeine blocks the receptors and prevents drowsiness. Our brain stays awake and we can fit more cram sessions throughout the night.

But the brain adapts to this lack of fatigue by creating more adenosine receptors. This means we start to need to take more caffeine to keep us alert—the start of an addiction.



At the same time, caffeine stimulates our body in other ways. It increases adrenaline, a hormone that speeds up our heart rate, increases blood flow, and opens up the airways in our lungs. It also stops another hormone, dopamine—associated with happy feelings—from being reabsorbed into the brain, which means you temporarily feel happier. Actually, caffeine and cocaine have a similar effect on the brain in terms of their effect on dopamine, although caffeine is not as aggressive.

Caffeine addiction starts when it begins to affect dopamine levels. The more exposed the brain is to dopamine, the happier we feel. This is why when someone stops drinking coffee after a few weeks of excessively drinking it, she feels withdrawal symptoms. Dopamine levels begin to decrease and fall back into its normal range, so we don’t feel as perky as we did with that warm cup of coffee.



There is a lethal limit to caffeine. However, the human body is filled with several tricks that prevent us from reaching a caffeine overdose. They found that approximately 150 mg per 1 kg of someone’s body weight can kill someone. To put it in perspective, if someone weighs 70 kg (154 lbs), they would need 14 g of caffeine to kill them. There’s about 200 mg in a medium Tim Hortons coffee, which means you’d need about 70 cups of it to reach that dose. Even the 260 mg in a tall Starbucks cup would require over 50 cups. And the human stomach can’t hold that volume.

But in any case, even before hitting four grams, the brain can begin to hallucinate and become hyperactive.



You can try to escape caffeine addiction by quitting cold turkey or by slowly weaning yourself off of it.

Many doctors recommend gradually reducing caffeine intake, as it can be harder to focus, be productive, and be happy if you quit cold turkey. Although it takes longer to be clean, the withdrawal symptoms aren’t as severe and the body doesn’t go through much of a shock.

The best rates for a reduced caffeine intake as you quit are approximately:

Coffee: quarter of a cup each day (drinking the same brand throughout)

Energy drinks: half a can every two days

Caffeinated pop: a can or half a bottle every two days

The occasional coffee or caffeinated drink doesn’t hurt the body, but like everything we take into our bodies, moderation is key.

Exams are tough, but an addiction is even harder to beat.