A study in The Journal of the American Medical Association found that after healthy people were given nasal drops containing a strain of cold virus, those with six or more types of social ties (including friends coworkers and fellow volunteers) were four times less likely to get sick than those with only one to three types of social relationships.
When researchers from University College London measured cortisol levels (one marker of chronic stress) in individuals 30 minutes after the subjects woke up, they found that the loneliest people had levels 21 percent higher than the most socially connected.
Socializing can give your mind a workout: According to one study, the more frequently people interacted with others, the higher they scored on cognitive tests. Plus, research in the American Journal of Public Health found that among older women, those who had daily contact with friends saw their risk of developing dementia reduced by 43 percent compared with those who had contact less than once a week. This may be because social interaction helps form new synaptic connections, staving off cognitive decline.
Lower Blood Pressure
Researchers have found that people with hypertension who feel they can open up to friends are a third less likely to have their condition go uncontrolled. In another study that tracked people for four years, those who were the least lonely could expect their blood pressure to be 14.4 points lower than that of those who were the most isolated.
In a small study in Psychological Science, researchers monitored college students' sleep patterns and found that those who reported feeling more connected to their peers fell asleep 14 minutes faster and spent 17 fewer minutes awake during the night than their more solitary counterparts did.