Close relationships with family and friends, we know, are important for our health and well-being. But what about the people who make up our broader social networks: the parents at school drop-off, the neighbor down the street or that colleague in another department who always makes you laugh?

While research on the benefits of social connections has generally focused on the importance of “strong ties,” or the intimate relationships we have with family and close friends, a growing body of research is shedding light on the hidden benefits of casual acquaintances, too. Surprisingly, these “weak ties” can serve important functions such as boosting physical and psychological health and buffering against stress and loneliness, researchers have found.

Weak ties can be online acquaintances such as Facebook friends. They may also include someone you see frequently but don’t know well — a gym buddy, a member of your church or synagogue, or someone you see at a regular volunteer activity.

“While most people can only keep up a few strong ties because of the time and investment they require, weak ties can number in the hundreds,” said Karen Fingerman, a professor at University of Texas at Austin, who has been studying the impact of such “peripheral” ties for the past 20 years.

Decades of research suggest that having a diverse network of strong and weak ties is physically and psychologically protective. Maintaining various social roles, such as being a spouse, best friend, colleague and, say, a member of a cycling club and the PTA, is associated with better cognitive functioning, better emotional and physical health, and a decreased risk of mortality in later life.

People with high levels of what psychologists call social integration — those who participate in a broad range of relationships that consist of both intimate and weak ties — tend to be healthier and happier. Fingerman said that we don’t know why wide networks have so many benefits, but a variety of reasons have been proposed: They help buffer against stress, keep us calmer and encourage positive health behaviors. They also can provide information that might land us a job or get us to the doctor faster.

New research highlights one way that diverse networks may influence our physical health. In a study published in the journal Health Psychology, researchers analyzed data from more than 4,000 people, ages 52 to 94.

The researchers wanted to see whether high levels of social integration were associated, over time, with less age-related loss of lung function, an important indicator of health and longevity. (Reduced lung function predicts mortality and disease outcomes, such as cardiovascular disease, asthma and other lung disorders.)

The researchers found that the more social roles people engaged in, the better their lung function four years later.

“Every additional social role protects you that much more,” said co-author Sheldon Cohen, the director of the Laboratory for the Study of Stress, Immunity, and Disease at Carnegie Mellon University. “Surprisingly, our data also found that low-intimacy roles, like being a volunteer or a club member, were as equally effective in protecting lung function as high-intimacy ones, like having a spouse or being a parent, which highlights the big impact a wide social network can make on your health.”

Cohen said belonging to all of these networks often motivates people to stay healthy so they can fulfill responsibilities to the people in their lives. And people in a wide network tend to encourage each other to engage in healthy behaviors.

While superficial relationships can’t take the place of intimate ones, research shows that weak ties can contribute to well-being — if we take the time to engage with them, said Gillian Sandstrom, an assistant professor of psychology at Britain’s University of Essex.

In one study, Sandstrom conducted an experiment in a busy urban coffee shop. The researchers recruited 60 participants and assigned half to make “small talk, make eye contact … and then have a brief conversation” with the cashier, while the other half were told to “avoid any unnecessary conversation.”

The researchers found that participants who had the brief discussion reported an increased sense of belonging and a boost in happiness compared with those who avoided conversations. Interacting with strangers as though they are weak ties, even for just a few moments, can open up sources of happiness in our day-to-day lives, said Sandstrom, “and help us to feel less alone.”

“Just as a diverse financial portfolio makes people less vulnerable to market fluctuations,” researchers wrote, “a diverse social portfolio might make people less vulnerable to fluctuations in their social network.” Even minimal relationships, they explain, can play a role “in fulfilling the fundamental human need to belong.”