Research has linked social isolation with shorter life expectancy. (iStock)

THE QUESTION Not exercising, being obese, smoking and abusing drugs are among the factors known to shorten people’s life spans. Might being lonely or socially isolated have a similar effect?

THIS STUDY analyzed data from 70 studies, involving 3.4 million people who were, on average, 66 years old at the start of their study. During the research periods, which averaged seven years, about 25 percent of the participants died.

People who reported being lonely were 26 percent more likely to have died than those who did not. Mortality risk was 20 percent higher for those who were socially isolated than for those who were not and 32 percent higher for people who lived alone vs. those who did not. The chance of having died during a study was also greater for middle-age adults who were lonely or lived alone than for those people of all sorts who were older than 65.

WHO MAY BE AFFECTED? People who live alone, have little social contact or generally feel lonely. The researchers found that the negative effect on longevity was the same for all people who were lonely — whether they were actually alone or they merely felt alone despite having a social network, described as objective and subjective loneliness, respectively.

CAVEATS The 70 studies used various methods and standardized scales to determine social isolation and loneliness, including some that relied on the participants’ responses. The analysis did not include data on how long people had been lonely, socially isolated or living alone. Most of the data came from older adults, with just 24 percent of the studies having an average age for participants of 59 or younger and 9 percent of the studies including people younger than 50.

FIND THIS STUDY March issue of Perspectives on Psychological Science

LEARN MORE ABOUT social isolation at (under “Issues Treated,” click “See More,” then “Isolation”). Learn about dealing with loneliness at (search for “loneliness”).

The research described in Quick Study comes from credible, peer-reviewed journals. Nonetheless, conclusive evidence about a treatment's effectiveness is rarely found in a single study. Anyone considering changing or beginning treatment of any kind should consult with a physician.