Americans begin their day with a fresh hot cup of coffee or tea because they claim it gives them the boost that they need to get going.
Besides being addictive, caffeine stimulates the brain in ways similar to amphetamines and even though it is much milder, it still stimulates the brain similar to that of a drug. Caffeine is linked to many cases of insomnia, as a matter of fact it is the biggest substance linked to insomnia. Another way that caffeine can hinder sleep is because it is a diuretic which stimulates the kidneys causing people to have to urinate more frequently than normal and very often throughout the night.
It is said that only 100-200 milligrams of caffeine can relieve drowsiness. Having said that, consider the following, 1 espresso has 200 mgs of caffeine, 1 cup of coffee has 100mgs of caffeine, a 12 oz can of cola has 45 mgs of caffeine, 1 Midol has 32 mgs and 1 Excedrin has 85 mgs. Now, take a look at this, a cup of decaf coffee only has 3 mgs of caffeine and since caffeine has no flavor, color or odor, there sure can't be any reason that you can not enjoy that cup of coffee any time that you want to and still be able to get to sleep at night.
Some people are sensitive to caffeine while others are not but if you find a relationship between a bad night's sleep and your caffeine intake, that does not mean that you can't enjoy a cup of coffee or even a cola, just make sure they are caffeine free. The most common sources of caffeine are coffee, cocoa beans, cola nuts, and tea leaves. The amount of caffeine that is in products depends on the serving size, the product, and how it is prepared. People differ greatly in their sensitivity to caffeine and many develop a tolerance for it.
Many people feel jittery from caffeine and learn very quickly to avoid caffeine after a certain time if they plan on sleeping. Caffeine increases the secretion of stress hormones such as adrenaline so if a person is already secreting higher stress hormones, then caffeine could cause a rapid increase that would definitely trigger a period of insomnia. People usually do not give a lot of thought to their caffeine intake but believe it or not, caffeine used to be used in clinical settings to induce panic attacks in patients.
Having said all of this, my opinion regarding caffeine is to avoid it when possible because overall, it's not great for your health, especially in abundance. There's nothing wrong with enjoying a cup of coffee, just know when to say when.