By Emma Wei

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As a coffee addict, I find myself fascinated by the small brown beans from which it is made. Did you know, for example, that coffee is the world’s most commonly used psychoactive drug?

Originating from Ethiopia, these beans made it across the Mediterranean, before reaching America in the 18th century, a country in which 146 billion cups of coffee are consumed every year, a statistic that makes us question just why coffee is so addictive.

It’s the caffeine which is responsible for the energy released by an espresso, for example, through its absorption and subsequent transportation to the brain. Firstly, because caffeine molecules have similar shape to adenosine, responsible for binding to receptors and causing fatigue. Because of their close resemblance, caffeine molecules are able fit into these receptors. This blocks the adenosine, avoiding the sense of tiredness. Therefore, caffeine is a stimulant for your brain that produces the feeling of alertness.

By blocking the adenosine receptors, caffeine also stimulates the brain by increasing the neuron firings (more action potentials are generated). The pituitary gland in your brain senses the change in activity, and releases the hormone adrenaline in response. This causes a ‘boost’ in energy by increasing heart rate and blood pressure.

Your dopamine level is also affected by caffeine - dopamine being a type of neurotransmitter usually associated with pleasure. Caffeine blocks the reabsorption of dopamine, therefore leading to an elevated dopamine level. This effect is similar to the use of many psychoactive drugs such as heroin and cocaine. This dopamine connection makes you feel good after coffee intake.

Continuous intake of caffeine can actually change your brain. The number of adenosine receptors increase over time to balance out the effect of caffeine, which makes your body more sensitive to the effect of adenosine. Studies have also found that the brain responds to caffeine by decreasing the number of norepinephrine receptors. This explains why the sudden withdrawal of caffeine can lead to a series of symptoms such as headaches, muscle pain, nausea and a depressed mood. The brain is at this point accustomed to the constant levels of adrenaline and dopamine, which make quitting caffeine so hard. It is, in fact, so difficult to cut down caffeine that a professor of neurology claimed that caffeine withdrawal should be classified as a psychological disorder.Coffee’s addictive nature even led it to recently be banned in South Korean schools in order to ‘improve performance’.

The power of coffee beans is almost mythical in nature, having even been banned several times in history. So the next time you enjoy a pot of coffee, appreciate the magical taste and enjoy the amazing biochemistry beyond it.