Loneliness is linked to poor physical and mental health and is a greater predictor of early death than obesity.
Because of such risks, researchers sought to determine whether loneliness was a lifelong trait, not a temporary state. In conducting the first genome-wide association study of loneliness, Prof. John Cacioppo and his colleagues confirmed previous studies showing that the risk for feeling lonely is partially due to genetics, but environmental influences play a bigger role. Their findings also concluded the genetic risk for loneliness is associated with neuroticism and depressive symptoms.
“Humans are fundamentally social animals. Just as physical pain alerts humans to potential tissue damage and motivates us to take care of our physical bodies, loneliness is part of a biological warning system that has evolved to alert us of threats or damage to our social bodies,” said Cacioppo, the Tiffany and Margaret Blake Distinguished Service Professor and director of the Center for Cognitive and Social Neuroscience. “Animal studies suggest that what is heritable is not loneliness per se, but the intensity of the social pain that occurs when there is a discrepancy between an individual’s desired and actual social connections.”
The study of more than 10,000 people was published last month in Neuropsychopharmacology. Cacioppo worked with researchers at the University of California San Diego, the Vanderbilt University Medical Center and Janssen Pharmaceutical.
Cacioppo and colleagues from the Netherlands have examined the heritability of loneliness in previous studies of identical twins, fraternal twins and siblings. These studies led to estimates of the heritability of loneliness ranging from 37 percent to 55 percent. Previous studies also tried to pinpoint specific genes that contribute to loneliness, focusing on genes related to neurotransmitters, such as dopamine and serotonin, or other cellular systems associated with human attachment such as oxytocin.
But such studies mostly relied on small sample sizes and have produced inconsistent results. Researchers in the new study used a much larger sample size, examining genetic and health information from 10,760 people aged 50 years and older collected by the Health and Retirement Study—a longitudinal study of health, retirement and aging. As part of this study, participants answered three well-established questions that measure loneliness. The study accounts for gender, age and marital status.
Researchers found loneliness, which was defined as the tendency to feel lonely over a lifetime, rather than just occasionally due to circumstance, is a modestly heritable trait—14 percent to 27 percent heritable from the additive effects of common variants. The researchers also determined that loneliness tends to be co-inherited with neuroticism and a scale of depressive symptoms.
Researchers are now working to find the specific set of genetic variants that underlie a person’s susceptibility for loneliness to gain additional insights into the molecular mechanisms.