Living alone or feeling isolated is one of the biggest causes of illness. It's equivalent to smoking 15 cigarettes a day, or to being an alcoholic, and it is twice as harmful as obesity, researchers say. Conversely, social connections with friends, family, neighbours and colleagues improve our chances of survival by 50 per cent. Researchers from Brigham Young University say that social isolation is one of the great, and yet unrecognised, risk factors in health. In making their discovery, the researchers analysed data from 148 studies that measured the frequency of human interaction with overall health over a seven-year period. They say that even the 50 per cent estimate may be conservative, and that the real risk of social isolation to our health could actually be far higher. (Source: PLoS Medicine, 2010; 7: e1000316).