In this piece on the New York Times Opinion Pages, Dr. Sack writes

Addiction has three main characteristics that cause it to be considered a disease. First, it has a lifelong course characterized by frequent relapses, cross addiction and a common set of behavioral changes. Second, like other chronic medical disorders, genetics plays an important role is determining who is at risk to become addicted. Finally, there are effective medications that treat drug addiction by blocking the rewarding effects of drugs and decreasing drug cravings.

Read the entire article here.