Negative symptoms experienced after drug use are known as withdrawals. What is happening, in essence, is your body is crying out for you to take more of the drug. And if you listen to your body and take the drug again, the withdrawal symptoms go away. Withdrawals are the result of a physical dependence on a drug. This physical dependence is the hallmark of addiction. And believe it or not, most of the world is addicted to a drug that resembles heroin in its effects, but is perfectly legal. That drug is caffeine. According to a John Hopkins Medicine study conducted in the mid-90s, it takes as little as little as a half cup of coffee a day to cause caffeine withdrawals. Caffeine withdrawal is beginning to be recognized by the medical community as a physical disorder. It is expected that the World Health Organization will update their ICD (International Statistical Classification of Diseases and Related Heath Problems), a kind of mental-disorder bible for the medical field, to include a diagnosis for caffeine withdrawal. The diagnosis should also appear the next Diagnostic and Statistical Manual of Mental Disorders.