'If you metabolise caffeine faster, then the levels in your body will change quickly and your physical reaction to it will be more pronounced, which triggers a psychological response,' says GP Dr Sarah Jarvis.

'Caffeine makes your heart beat faster and if you start to focus on it, more adrenalin is released, which will make you feel anxious, light-headed, hyper and dizzy - similar to what you may feel after drinking excessive alcohol.

'The 'come-down' is then the post-adrenalin effect.'