During Murthy’s early years as a doctor at Boston’s Brigham and Women’s Hospital, he noticed things about his patients that were not strictly medical—namely, their social isolation. While some patients were surrounded by family and friends, others went for weeks without visits or phone calls from the outside world. Some died alone. Murthy also noted that his patients yearned for companionship, which alerted him to the link between health and loneliness. James, a patient with diabetes, brought this connection into sharper focus. James quit his job as a baker and moved to an affluent enclave after winning the lottery. His health problems grew alongside his distance from other people. Patients like James made Murthy realize that social connection is integral to human health.

Murthy defines loneliness as a lack of social connection and an absence of closeness, trust, and affection from other people. He describes three types of loneliness: 1) Intimate loneliness, or the longing for a romantic partner and close friends; 2) Relational loneliness, or the desire for social companionship; and 3) Collective loneliness, or the hunger for a network of people with common interests and a shared sense of purpose.