Caffeine-filled cups of tea and coffee do not really provide the boost to mood and alertness that people think - they just beat withdrawal symptoms.
New research by Dr Peter Rogers, a psychologist from the University of Bristol, shows that caffeinated drinks have a "pick-me-up" effect only because they counter the tiredness, headaches, and slowing of reactions caused by withdrawal from caffeine in the first place.
Dr Rogers and his team found that caffeine gave the biggest lift when people were suffering from overnight caffeine withdrawal symptoms.
They conducted studies in which they gave people fruit juices with caffeine, and compared this with what happened when people were given a drink with no caffeine.
Not surprisingly, when they felt the caffeine-induced lift, people preferred the drink.
Source BBC News