Whether it’s a shot of espresso or a milky cappuccino, the process of caffeine consumption begins in the gut. Once there, it has a direct stimulating effect on your brain cells due to its close resemblance to adenosine, a molecule that has a relaxing effect on the central nervous system. This allows caffeine to fit into adenosine receptors in the brain, blocking and preventing the feeling of fatigue.

“Caffeine is a stimulant,” Dr Athwal explains. “It increases the circulation of chemicals such as cortisol (the stress hormone) and adrenaline (prepares your sympathetic nervous system in response to a stressor or threat) in the body. Caffeine builds up the adrenaline supply, increasing our heart rate, pumping the blood, and opening up the airways. It also prevents dopamine from getting reabsorbed back into your system, leaving the feel-good chemical hanging around in your brain longer.”

As a result, natural stimulants such as dopamine work more effectively, which in turn tells your brain that your cup of coffee is good and that it needs more of it. No wonder we’re so hooked.

“Caffeine intake has been shown to ‘chronify’ headache disorders, including migraines,” consultant neurologist Dr Mona Ghadiri-Sani tells Stylist. “You will notice a rebound headache when you are due for you next ‘fix’, with worsening headaches that improve after the intake of caffeine.

“Over time, you may find that you need higher quantities or stronger doses to achieve the same outcome. Headache aside, you may also experience associated fogginess, fatigue, poor sleep, poor concentration, light and noise sensitivity and so on. Before long, you may be left with a constant foggy head with no crystal clear days.”

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