Addiction is a brain disease, just as diabetes and cancer are diseases. It can not be defined as a simple weakness. Anyone can develop an addiction; it does not matter your background, race, gender or socioeconomic status. Addiction can happen at any age, but usually starts when a person is young. When a drug user can't stop taking a drug even if he/she wants to, and the urge is too strong to control, it's called addiction; easily defined by its craving, seeking, and use even when the results are extremely negative.
Addiction can become more important than the need to eat or sleep and the urge to get and use the drug can fill every moment of a person's life. The addiction replaces all the things the person used to enjoy. When people start taking drugs, they don't plan to get addicted, they believe they can control how much and how often they take the drug. But drugs change the brain. Drug users start to need the drug just to feel normal. That is addiction, and it can quickly take over a person's life.
It can be extremely difficult for people to stop on their own, and in many cases, impossible. Long-term alcohol and drug use results in significant changes to brain function. These changes persist even after the person stops using drugs. The drug and alcohol induced changes in brain function have behavioral consequences, one of which is the continual use despite negative consequences. This understanding of addiction and its effects to the makeup of a person explain why an individual has difficulty in achieving abstinence without proper treatment.