Caffeine is found in coffee, tea, chocolate, soft drinks, and some nuts. It's not an essential nutrient, but try telling that to someone who hasn't had that first cup of coffee in the morning. Caffeine has a stimulating effect upon the central nervous system (CNS), and even though researchers keep trying to implicate caffeine in heart disease, the American Heart Association (AHA) reports that no studies have been conclusive in linking moderate caffeine consumption to coronary heart disease. Moderate drinking was defined as one to two cups per day.
Consuming caffeine up to eight hours before bedtime, however, can adversely affect your sleep. Since insomnia and other sleep disorders are symptoms of depression, it makes good sense to limit your caffeine intake to earlier in the day. Also, caffeine is an appetite suppressant, so if your depression is keeping you from eating well, you may want to limit your intake of caffeine.
If you drink caffeine on a regular basis and then abruptly stop drinking it, you may experience “caffeine withdrawal.” Symptoms include primarily headache, along with anxiety, fatigue, drowsiness, and depression. Interestingly, researchers have found that the post-surgery headache many people experience has nothing at all to do with the operation. It's caffeine withdrawal! You head into surgery on an empty stomach — no food or drink after midnight, has been the standard protocol. Now, to relieve that symptom, many hospitals will permit you that cup of java.