Editor's note: This popular story from the Daily Briefing's archives was republished on May 11, 2023.

Research has found that loneliness and social isolation are associated with an increased risk for conditions like anxiety, depression, heart disease, and stroke. In fact, a 2010 meta-analysis found that loneliness is as harmful to physical health as smoking 15 cigarettes a day—meaning friendship to mitigate loneliness is good for you. Writing for the New York Times, Catherine Pearson uncovers just how many friends research suggests you should have.

How many friends should you have?

According to Jeffrey Hall, a professor of communication studies at the University of Kansas, if you want to mitigate the health impacts of loneliness, the most important thing you can do is have at least one important person in your life.

"Going from zero to one is where we get the most bang for your buck, so to speak," Hall said. "But if you want to have the most meaningful life, one where you feel bonded and connected to others, more friends are better."

Robin Dunbar, a psychologist and anthropologist, found in his research that human beings are able to maintain about 150 connections at once, which includes a group of around five close friends, followed by circles of more casual friends.

Other research has come up with similar numbers, Pearson writes. One study from 2016 found that those with at least six friends have better health throughout their lives, and a study from 2020 found that middle-aged women who have at least three friends typically had higher levels of overall satisfaction with their lives.

How do you know if you need more friends?

To figure out whether you need more friends in your life, psychologist Marisa Franco recommends asking yourself, "Do I feel lonely?"

"Loneliness is sort of a signal or alarm system," Franco said. While everyone feels lonely sometimes, you should determine whether you feel left out or isolated regularly, Pearson writes.

Franco also recommends asking yourself if there are parts of your identity that you feel are restricted.

"Different people bring out different parts of us. So when you have a larger friend group, you're able to experience this side of yourself that loves golf, and this side of yourself that loves cars, and this side of yourself that loves flowers," Franco said. "If you feel like your identity has sort of shrunk, or you're not feeling quite like yourself, that might indicate you need different types of friends."

Since making new friends as an adult can be difficult, Franco said it's often easier to rekindle old relationships. She added that you should take the initiative and not assume that friendships will simply happen organically. However, it's also important to not spend too much time with friends you feel ambivalent about, as research has found that can also be bad for your health, Pearson writes.

Ultimately, there "isn't a magic number" of friends for everyone, Hall said. "Your personality and the characteristics of your life are going to make a difference." (Pearson, New York Times, 5/9)