Most of us put up with whiners, naggers, control freaks and other annoying people in our lives for good reason - we're related to them.
Researchers at the University of California, Berkeley, and Bar-Ilan University in Israel sought to understand the reason people don't just ditch the difficult or demanding people in their families and wider social networks.
Their findings, recently published in the American Sociological Review, show that when it comes to toxic relationships, blood can be thicker than water.
Participants surveyed for the study were more apt to report that the most difficult people in their lives were female family members such as wives, mothers, and sisters.
That said, close female kin may be disproportionately named as difficult because they are more likely to be actively and emotionally involved in people's lives, researchers said.
"The message here is that, with female relatives, it can be a two-sided thing. They may be the people you most depend on, but also the people who nag you the most," said study senior author Claude Fischer, a sociology professor at UC Berkeley. "It's a testament to their deeper engagement in social ties."
Overall, the findings show that, on average, about 15 percent of the relationships that survey takers talked about were categorized as difficult, and that their conflicts were most often with close kin such as parents, siblings and spouses.
Friends were least likely to be difficult, representing about 6 or 7 percent of the annoying members of social circles for both younger and older adults.
"The results suggest that difficult people are likely to be found in contexts where people have less freedom to pick and choose their associates," said study lead author Shira Offer, a professor of sociology at Bar-Ilan University.
The researchers analyzed relationship data from more than 1,100 younger and older adults in the San Francisco Bay Area, more than half of whom are female, using the University of California Social Networks Study (UCNets), of which Fischer is the principle investigator.
Launched in 2015, the multiyear UCNets survey uses face-to-face and online interviews to assess how people's social connections affect their health and happiness.
"It's commonly agreed that maintaining strong social ties is healthy," Fischer said. "But social ties can be as much a source of stress as a source of joy, and so it's important to understand how different relationships affect our health and well-being."
For their investigation, Offer and Fischer studied more than 12,000 relationships that ranged from casual friendships to work relations to close family bonds.
Participants were asked to name the people with whom they engaged in different social activities and, of those, identify the ones they found difficult or burdensome.
The relationship categories were divided into "difficult only," meaning ties that participants mentioned solely as difficult, and "difficult engaged in exchange ties," meaning relationships that are considered difficult but that also include confiding in, and giving and/or receiving emotional and practical support.
Younger people aged 21 to 30 named more "difficult engaged" people in their lives (16 percent) than the older cohort. They most frequently described sisters (30 percent), wives (27 percent), and mothers (24 percent) as being burdensome, and to a lesser degree fathers, brothers, boyfriends and roommates.
Older people in their 50s, 60s and 70s identified about 8 percent of the people in their social networks as "difficult engaged." Topping their list were mothers (29 percent), female romantic partners (28 percent) and fathers and housemates tied at 24 percent.
As for relationships with co-workers and other acquaintances, younger people named a little over 11 percent of those connections as difficult only. For older people, that number was slightly higher, amounting to 15.5 percent of acquaintances and 11.7 percent of co-workers.
Overall, workplaces were hotbeds of trouble, but not of the "difficult engaged" kind. And, as for why we don't rid our lives of difficult people:
"Whether it's an alcoholic father whom you want to cut ties with, an annoying friend with whom you have a long history or an overbearing boss, relationships are complicated and in many cases unavoidable," Fischer said.