Drug Addiction

Drug addiction is considered by experts as a pathological state. The disorder of dependency involves the progression of acute drug usage to the development of drug-seeking conduct, the vulnerability to regress to drug use again, and the diminished, slowed ability to react to naturally gratifying stimuli. The Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) has categorized three stages of addiction: preoccupation/anticipation, binge/intoxication, and withdrawal/negative affect.   

These stages are characterized, respectively, by continuous cravings and obsession with obtaining the substance; using more of the substance than needed to feel the intoxicating effects; and experiencing tolerance, withdrawal symptoms, and decreased inspiration for normal life activities. By the American Society of Addiction Medicine meaning, drug addiction differs from drug dependence and drug tolerance. 

Quite simply Drug addiction is compulsive consumption of a substance in spite of the negative effects which can be severe; substance abuse is simply inordinate use of a drug or use of a drug for intentions for which it wasn't medically intended for.