According to Elizabeth Hartney PhD., "For a long time, addiction meant an uncontrollable habit of using alcohol or other drugs. More recently, the concept of addiction has expanded to include behaviors, such as gambling, as well as substances, and even ordinary and necessary activities, such as exercise and eating. The key is that the person finds the behavior pleasurable in some way and engages excessively in the behavior as a way of coping with life."

Dr. Hartney provides an overview of the concept of addiction, and explains the two aspects that all addictions have in common.