Susceptibility to lonlieness (a state of feeling lonely) may be less about genetics than thought.
"For two people with the same number of close friends and family, one might see their social structure as adequate while the other doesn't," Palmer said. "And that's what we mean by 'genetic predisposition to loneliness' -- we want to know why, genetically speaking, one person is more likely than another to feel lonely, even in the same situation."
The heritability of loneliness has been examined before, in twins and other studies of both children and adults. From these, researchers estimated that 37 to 55 percent of loneliness is determined by genetics. 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, Palmer said, these studies mostly relied on small sample sizes.
In their latest research, Palmer and team used a much larger sample size -- they examined genetic and health information from 10,760 people aged 50 years and older that was collected by the Health and Retirement Study, a longitudinal study of health, retirement and aging sponsored by the National Institute on Aging at the National Institutes of Health. As part of this study, participants answered three well-established questions that measure loneliness. The survey doesn't actually use the word "lonely," as many people are reluctant to report feeling that way. Instead, the questions were:
How often do you feel that you lack companionship?
How often do you feel left out?
How often do you feel isolated from others?
The study accounted for gender, age and marital status, as married people tend to be less lonely than unmarried people.
Here's what Palmer's team found: Loneliness, the tendency to feel lonely over a lifetime, rather than just occasionally due to circumstance, is a modestly heritable trait -- 14 to 27 percent genetic, as compared to the previous estimates of 37 to 55 percent. This new estimate of the genetic contribution to loneliness could be lower than previous estimates because Palmer's team relied on chip heritability, a method that only captures common genetic variations and not rare genetic variation.
The researchers also determined that loneliness tends to be co-inherited with neuroticism (long-term negative emotional state) and a scale of depressive symptoms.
https://www.sciencedaily.com/releases/2016/09/160920115629.htm
