Cal Newport, Digital Minimalism: Addiction is a condition in which a person engages in use of a substance or in a behavior for which the rewarding effects provide a compelling incentive to repeatedly pursue the behavior despite detrimental consequences. Until recently, it was assumed that addiction only applied to alcohol or drugs: substances that include psychoactive compounds that can directly change your brain chemistry. As the twentieth century gave way to the twenty-first, however, a mounting body of research suggested that behaviors that did not involve ingesting substances could become addictive in the technical sense defined above.
Ibid.: Phones have become woven into a fraught sense of obligation in friendship. . . . Being a friend means being “on call”—tethered to your phone, ready to be attentive, online.