Addiction is the dependence on a substance such as drugs or alcohol, or an action such as sex, work, the internet, pornography, etc. Addictions can be pleasurable at first, but over time the addiction interferes with ordinary life responsibilities, such as work, relationships, and health.
People compulsively use drugs, gamble, or shop nearly always in reaction to being emotionally stressed. Emotional stress can be caused by traumatic memories, anxiety, stress at work or in the home, thoughts of hopelessness or worthlessness, etc. The only way the addict has learned to cope with the emotional stress in their life is by escaping it through their addiction. Over time alcoholics and drug addicts develop a physical dependence to the substance. In other words they no longer use just to cope with emotional stress, they use because their brain and body require it in order to function.
Treating addiction requires an understanding of how it works psychologically. It is important to recognize that an addiction’s cause is not simply a search for pleasure. It has nothing to do with a person’s morality, willpower, or character. Treatment requires education on how the brain is effected, creating new coping skills to deal with emotional stress, and processing the deeper psychological issues that are causing the emotional stress.