In large doses, caffeine can produce headaches, jitters, nervousness and even delirium. This is especially so for someone not used to taking caffeine. Caffeine also stimulates the secretion of gastric acid and increases urination. Most researchers agree that there is very little health risk when less than 600mg of caffeine is consumed a day. Regular use of more than 600 mg of caffeine per day can cause chronic insomnia, persistent anxiety, depression and stomach upset.
People can become dependent on caffeine.
This means they have a strong desire to have caffeine because it has become important in their daily lives. If caffeine is unavailable they may panic or feel anxious. People who are dependent on caffeine may experience withdrawal symptoms such as headaches, irritability and a feeling of tiredness if they stop or dramatically cut down their caffeine intake. Make A Noise.