Addiction is defined as an urge to do something, such as an activity or a drug, repeatedly, without taking care of the consequences.
For example, a a cocaine addict may still continue to abuse the narcotic even after having been caught purchasing coke in an infamous part of town. Or cigarette user might continue to use tobacco products even after having been diagnosed with cancer of emphysema.
Addiction can arise in two ways - as a physical effect or through the mind.
Often with a physical addiction, the addict will undergo physical withdrawal effects after the person attempts to quit the drug in question. This is very common with opiates, like heroin or narcotic pain medications. Still other substances that can lead to physical repercussions on withdrawal are alcohol, barbiturates (several outdated classes of sleeping medications), nicotine products and benzodiazepines (Xanax, Valium, Ativan, BuSpar, Halcion, Anafranil, etc.) In some cases, the withdrawal effects will lead to severe seizures, such as in the case with benzos. People who have a physical dependency on an addictive substance will often take the substance, not to derive satisfaction after a certain point, but more so to subdue withdrawal effects. Physical dependency is occasionally described as as physiological tolerance.
Psychological addiction affects addicts differently in that a drug user will use a drug more for the satisfaction that the user first extracts from it more than any other aspect of the drug’s effects. The substance in use will normally affect the the user’s brain function and expel pleasure increasing chemicals that result in the further use of the drug. This results in a continuous process that the user considers extremely complicated to end.