caffine addiction can be bad but it cant kill you unlike other substances, at least it keeps you awake if you are tired, there are other worse addictions, tobacco, alcohol even marijunana. alcohol and tobacco are very common and are the worst addictions both can kill you, tobacco, heart disease, lung cancer. alcohol, stroke, Cirrhosis of the liver, pancritiis, mouth, throat and stomach cancers not to mention, personal problems, trouble with the law, drinkin and driving, abuse and person relationship problems. be glad that caffeine isn't as bad as others cant say about mary jane I have no idea what it does but it is illegal so im sure its not great.