We know that having a solid group of friends can make your life more fun, but it can also improve your health and help you live longer. Let us count the ways.

Birds of a Feather Flock Together

Look at your friends and you’ll see yourself. Research shows that people tend to hang out with others of their same body type—but they can’t pinpoint why. Matthew Andersson, PhD, is an assistant professor of sociology at Baylor University in Waco, Texas. He conducted a study when he was at Yale and told Health Magazine that friends “may include shared activity habits, shared eating habits, shared recreational or leisure activities, or shared norms, expectations or preferences that others may have for one’s behavior or appearance.”

Similarly, smokers and drinkers pal around together. It’s not clear if they’re picking up habits from others or seeking out friends with whom they can socialize with in those ways, but research also shows that if you want to quit a bad habit, it’s easier to do it in a group. A Harvard study finds that smokers in social groups tend to influence each other to stop—and that influence can spread when a person in one group also belongs to another, essentially acting as a “carrier.” “What people need to understand is that because our lives are connected, our health is connected,” says an author of the study, Nicholas Christakis, a member of Harvard Medical School’s Department of Health Care Policy.

People in Groups Have Less Stress

Your stress levels improve when you don’t go it alone. Friends can help you navigate through difficult times in your life, such as divorce, illness or death of a loved one. They can foster a sense of belonging and can make you feel needed—and all that reduces risk of depression, anxiety and high blood pressure.

A study published in the Journal of the American Osteopathic Association shows that medical students who worked out in a group had lower perceived stress and higher quality of life than those who didn’t. Another study that looked at stress-hormone levels in elementary-school aged children found kids who had a negative experience with a best friend around had lower levels of cortisol and higher self-worth than those who didn’t have a buddy nearby.

Your Workout Improves

When you work out with friends, you add elements of accountability, motivation and enjoyment that you might not find by yourself. Multiple studies have shown that those who have social support for exercise—a significant other, someone you work out with on a regular basis, a friend you text when you’ve hit a milestone, or even a Facebook group where you can share progress—are doing better than those who lack any support. However those who feel like they’re being coerced into joining a gym or going out for a jog are actually less likely to do it.

Friends Help Your Brain

Having a strong social group can improve your brain health and slow the progression of diseases such as dementia. A recent Ohio State University study looks at the hippocampus region of the brain in two groups of mice: The first group lived with six other mice friends, and the second group was paired with only one other mouse—an “old couple” model. The mice were 15 to 18 months old, about the human equivalent of old age, when the memory starts to decline.

What the researchers found when they gave the mice memory tests was that the subjects with the larger social group performed better, again and again. The mice that were in pairs had increased inflammation around the brain, which signified eroding cognitive function.

“Our research suggests that merely having a larger social network can positively influence the aging brain,” says Elizabeth Kirby, an assistant professor of behavioral neuroscience and member of the Center for Chronic Brain Injury at Ohio State.

Kirby added that as we get older, we should make choices about where to live based on proximity to a larger social group. “A lot of people end up isolated not by choice, but by circumstance. ‘Over the river and through the woods’ might be fun for the kids, but it’s probably not so great for Grandma.”