It means that when you take drugs and are addicted you do not get high anymore. Your body has become so dependent on drugs that you need that drug to survive, otherwise you will be what is called...
You can not be psychologically dependent on a drug. Dependence is a medical term form for a person who physically withdraws when they stop the use of a drug. Now if you are psychologically addicted...
The word drug means: something you get from a pharmacy, like medication advice/help etc... or it could be a drug like cocaine, marijuana etc... actually, any substance that changes the bodies regular...