Caffeine is a psychoactive substance that is widely seen as a performance enhancer. It can be found in coffee, thee, many sugared soda’s, chocolate, candy and pastry, and energy drinks. It has become indispensable at the breakfast table and a habitual 'partner in crime' at work. It exists in all kinds of flavors, and has been lifted up to a form of art by the current baristas. Coffee has become interlinked not only with performance, but also with taste and refinement, like wine. I have to admit that I’m writing this on a Thursday morning, with a delightful cup of steaming coffee next to my laptop. One of the few I allow myself this week. I worked late in the practice last night and in this case I can use a cup of stimulation to get me going. Not to improve my performance, but rather to compensate decreased performance due to sleep shortage and fatigue (I know, even I am human!). The danger lies in making a habit of this, in which case I will never focus on the real causes of my sleepiness or fatigue, but rather cover it up with a stimulant that is also known to induce sleep- and fatigue complaints when reducing intake. Talking about a vicious cycle! But let’s begin by first taking the physiological elevator downwards and explain the working mechanisms of caffeine and how this influences sleep and wake.

Caffeine is a stimulant, that peaks approximately 45 minutes after intake and has a half-life of 3 to 7 hours. A half-life refers to the time necessary to decrease the concentration of a substance in the body by half. People with a rather slow metabolism will still have half of the concentration present in their brains after 7 hours. The speed of metabolizing also decreases with increasing concentration. So, the more caffeine you consume, the slower you get rid of it. This might seem as a very interesting mechanism to increase performance, however, there are consequences! The main working mechanism of caffeine is blocking adenosine recepetors in the brain. Adenosine is a substance that signals our ‘hunger for sleep’, our sleep pressure, which has a general ‘slowing-down’ effect in our brain. It decreases our performance as a way of signaling that it is time to slow down and eventually sleep. A receptor is like a keyhole for specific substances in our brain. It enables them to activate and have an influence. Adenosine is the key that fits this keyhole, the adenosine receptor. Caffeine will block these receptors and as such the working mechanism of adenosine. Essentially, it masks our sleep need and as such sleepiness, while at the same time, adenosine keeps on accumulating in the brain (because it is produced by mere wakefulness). As long as these receptors are blocked by caffeine, we feel less sleepy, and seemingly unaware of an accumulating sleep pressure. The result is a ‘tsunami’ of adenosine suddenly connecting with all the receptors when caffeine is finally metabolized, the so-called caffeine-crash. The sudden feeling of sleepiness, fatigue, distorted attention and focus, which results in a decreased general performance. As such, most people tend to compensate for their decreased performance by grabbing the nearest caffeinated beverage. 

Caffeine also has a stimulating effect on the stress system by increasing the production of cortisol, a stress hormone. Research shows, however, that this cortisol increase already disappears after one week of moderate caffeine intake (3units/day), which is called the tolerance development. After this short period, a higher dose is needed to experience the same effect. Moreover, a withdrawal of caffeine for more then 24 hours already results in withdrawal effects such as headache, fatigue, sleepiness, less energy, depressed mood, attentional problems, irritation and feeling weary and unrefreshed. All these symptoms often lead to increased caffeine intake in order to compensate for the deteriorating effects they have on performance, which leads to a vicious cycle. Beware, the effects of caffeine on the working mechanism of adenosine continues, even when performance decreases. As such, people tend to increase their caffeine intake, which in turn decreases the time to metabolize it. So you get rid of it even slower! When we go to bed with caffeine still in our system, it takes longer to fall asleep, reduces our amount of deep sleep as well as our total sleep time. This will in turn lead to less recuperation during sleep, resulting in more fatigue and sleepiness in the morning.  The following performance decrease will in turn trigger a need to compensate with a new shot of caffeine. And we are back at square one…

Our advice is to avoid as much as possible (or completely) the daily use of caffeine. It is worth the effort to install other habits and choose decaffeinated coffee or thee, if you prefer a hot beverage. Give it at least a week and you will notice the difference. Your attention and focus will be more stable, you will not suffer from the typical performance decrements due to caffeine-crash. Your need for sleep or rest will be more easily detected, but this also means you can target the correct factors and mechanisms, instead of covering them up. your sleep and sleep quality will improve and you will optimize your recuperation. If, for some reason, you get yourself in a situation where you actually really can use a attentional boost, that delightfull cup of coffee will work like a charm. Just make sure you consume it before 2 pm, since you really want it to be completely out of your system when going to bed.

And don’t forget, physical activity and exposure to sunshine are often as stimulating as a cup of coffee, without all the side-effects! Make sure you use a varied approach in keeping your performance top notch!

Good luck!

Aisha Cortoos
Clinical Psychologist – Psychotherapist – PhD in Psychology
Sleep/stress expert