Caffeine is the most consumed stimulant in the world,
It is consumed in the form of coffee and tea.
At present there is no scientific data for promoting or discouraging coffee and/or tea consumption in the daily diet.
Short term benefits include mental alertness and improved athletic performance.
Short term adverse effects including headache, anxiety, tremors, and insomnia.
Long term adverse affects include generalized anxiety disorder and substance abuse disorders.
Long–term benefits are dose–dependent. Caffeine is associated with a reduced risk of Parkinson disease, Alzheimer disease, alcoholic cirrhosis, and gout. Both caffeinated and decaffeinated coffee are also associated with a lower risk of type 2 diabetes.
Heavy coffee intake may trigger coronary and arrhythmic events in susceptible individuals, although coffee intake is not considered a long–term risk factor for myocardial disease.
Most studies show a modest inverse relationship between coffee consumption and all–cause mortality.
Caffeine withdrawal is a well–documented clinical syndrome with headache being the most common symptom. (Source: Uptodate)