It’s long been known that elderly people are more prone to depression and other mental-health problems if they live on their own. New research suggests the same pattern may also be found in younger, working-age adults.

In a study of nearly 3,500 men and women ages 30 to 65, researchers in Finland found that people who lived alone were more likely that their peers to receive a prescription for antidepressant drugs. One-quarter of people living alone filled an antidepressant prescription during the seven-year study, compared to just 16% of those who lived with spouses, family, or roommates.

“Living alone may be considered a mental-health risk factor,” says lead author Laura Pulkki-Råback, Ph.D., a lecturer at the University of Helsinki’s Institute of Behavioral Sciences. The study was published today in the journal BMC Public Health.

The findings show only an association, not cause and effect, which raises a chicken-or-egg question: Does the experience of living alone lead people to become depressed? Or are the depression-prone more likely to live alone because of their temperament, preference, or difficulty with relationships?
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Both explanations are plausible, and both may play a role in any given situation, the researchers say.

Surveys of the study participants suggest that solo living may weaken social networks and produce “feelings of alienation from society” that could steer people toward depression, Pulkki-Råback says. “People living alone were more cynical in their attitudes,” she explains. “Being cynical and living alone may predispose to hopelessness and negative feelings, ultimately leading to depression.”

On the other hand, she adds, “Cynical people may also have ended up living alone because they are difficult to deal with.”

John Newcomer, M.D., a professor of psychiatry at the University of Miami Miller School of Medicine, says depression and feelings of isolation usually go hand in hand, and it’s not always clear which comes first.

“Being depressed certainly can cause you to not only feel, but [also] become, more isolated,” he says. “You feel hopeless that you’re ever going to be able to have relationships, but even at another level, you…just don’t feel like getting up and going out. You’re undermotivated to do the various steps that are necessary to achieve social engagement.”