University of Chicago social neuroscientist John T. Cacioppo unveils his pioneering research on the startling effects of loneliness: a sense of isolation or social rejection disrupts not only our thinking abilities and will power but also our immune systems, and can be as damaging as obesity or smoking. A blend of biological and social science, this book demonstrates that, as individuals and as a society, we have everything to gain, and everything to lose, in how well or how poorly we manage our need for social bonds.