In a very famous epidemiology study, one of the most referenced of its kind because of its impressive sample size, researchers Dr. Lisa Berkman and Dr. Leonard Syme studied seven thousand residents of Alameda County, California. All of them were observed for a nine-year period in order to discover all the common denominators among the healthiest residents. The researchers controlled for gender, race, ethnicity, socioeconomic status, alcohol, tobacco, obesity, depression, and medical care. The study showed conclusively that the healthiest people were the ones with the greatest quantity and quality of social support. And conversely, the most socially isolated people had the greatest morbidity (rate of disease) and mortality. A large social support network and high frequency of contact directly correlated with health and made all the difference between health and illness.
In an eight-year follow-up of the Alameda County study with 6,848 of the initial seven thousand subjects, the researchers found results consistent with the first study: a very strong correlation between the amount and quality of social support and reduced morbidity and mortality of all causes. Those who lived fairly isolated lives had a mortality rate that was three times greater than that of those who had family or friends. The researchers also found a very robust inverse correlation between the quantity and quality of social support and cancer. Those who were most socially isolated had a significantly greater chance of developing cancer and dying from it.
In another famous study, epidemiology researcher Dr. James House and his team conducted a prospective study of 2,754 residents of Tecumseh, Michigan, observing their social ties and group activities for ten years. This was a very rigorous study in that residents with any medical or psychiatric condition that could possibly interfere with their ability to be active in a social community were excluded from the study. Over time it became clear that people with the greatest participation in a social support network or group were the healthiest. Those who initially had great support but who, because of various life circumstances, lost their connection to community were found to develop a variety of health problems. Those with the least social support were found to have four times the mortality rate of those with the most support.