Addiction is a disease of the brain that causes dependence upon or a persistent, compulsive need to use a habit-forming substance or an irresistible urge to engage in an activity, despite harmful consequences. Addictions are characterized by the increasing need for more of the substance or activity to obtain the same effect. Abstinence from the addiction may cause unpleasant or even life-threatening withdrawal symptoms.
Sternberg, Barbara S., et al. "Addiction." The Gale Encyclopedia of Medicine, edited by Jacqueline L. Longe, 5th ed., Gale, 2015. Health & Wellness Resource Center, http://link.galegroup.com/apps/doc/NZWCER048901136/HWRC?u=vol_h58hs&sid=HWRC&xid=f1e1cf3a. Accessed 7 Dec. 2018.