Caffeine is a stimulant, which means it stimulates the brain and neurological system. It also stimulates the circulation of hormones in the body such as cortisol and adrenaline. Too much caffeine can cause nervousness irritability mood swings depression. Caffeine is found in many products we use every day without even thinking about it: coffee tea chocolate milk shakes etc. The average person consumes 5-6 cups of coffee per day, which contains about 200 mg of caffeine. This amount is more than enough to have an adverse effect on some people. In terms of effectiveness as a cognitive enhancer caffeine is a very weak drug with slow effects. Some people may feel focused alert after two cups of coffee but these effects only last for a few hours. For other people it has no effect at all. Caffeine is also known to cause heartburn stomach pain headaches when consumed in large amounts over long periods of time. So, too much caffeine can be harmful you should avoid drinking more than 3-4 cups of coffee per day. As a cognitive enhancer caffeine is not very effective but it's safe to say that it's not dangerous either.