Loneliness may partly be a genetic legacy, scientists report in Behavior Genetics.

They’re not talking about occasionally feeling lonely in the wake of difficult life events, such as the loss of a loved one. It’s normal to experience the full range of emotions, including loneliness, over time.

Instead, the researchers tracked loneliness over more than a decade in thousands of young adult twins in the Netherlands.

They estimate that genes may account for up to nearly half of the differences in loneliness they saw in their study.

The researchers included Dorret Boomsma, a professor at Vrije Universiteit in Amsterdam.

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Tracking Loneliness

Boomsma’s study included more than 8,300 identical and nonidentical twins. Twins are often studied to try to tease out genetic and environmental influences.

Here’s the reasoning behind that. Identical twins share all of their genes. Nonidentical twins share half of their genes. If twins are raised in the same conditions, their genetic traits may stand out.

In the loneliness study, the twins got surveys by mail every three or four years, starting around age 17. They rated how strongly they agreed or disagreed with statements such as “I feel lonely” and “Nobody loves me.”

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Inherited Trait?

Some twins reported feeling lonelier than others. Genes account for nearly half of those differences, the researchers estimate.

About half of identical twins and nearly a quarter of nonidentical twins shared similar characteristics of loneliness, write Boomsma and colleagues.

While not dismissing environmental influences -- such as how parents respond to children -- the researchers didn’t find any particular environmental factors that explained the results.

The genetics of loneliness seemed to treat men and women similarly. The same genes may influence loneliness in both sexes, write the researchers.

They note that loneliness studies in kids showed similar results. But Boomsma’s team didn’t dig into DNA to look for loneliness genes.

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Personal Loneliness Level

Perhaps people have a “set point” for loneliness, write the researchers.

In other words, there may be a loneliness level for each person. People may rise above or dip below that set point as their lives unfold, driven both by genetic and environmental influences.

That’s just a theory. It’s not absolute and certainly shouldn’t make anyone feel doomed to being lonely.

Reaching out to others, joining groups, and avoiding isolation may help you build a rich network. Being less lonely could also boost your immune system, other researchers reported in May.

By Miranda Hitti, reviewed by Louise Chang, MD

SOURCES: Boomsma, D. Behavior Genetics, Nov. 4, 2005; online edition. News release, University of Chicago.