Feelings of loneliness are often caused by social isolation, but a person may be surrounded by people and still experience feeling alone. Some people, such as extroverts, may need more social interaction than others to avoid feelings of loneliness, "especially if those relationships are not emotionally rewarding. In fact, Dr. Carla Perissinotto and colleagues at the University of California at San Francisco reported in 2012 that most lonely individuals are married, live with others and are not clinically depressed" (Brody, 2017). Loneliness has become a health crisis as recent studies link loneliness to higher cardiac disease, smoking, and mortality ((Gerst-Emerson et. al., 2015).