1. They reduce your stress when times are tough.
Breaking up with your ex (again)? Being with a BFF during a stressful time reduces levels of the stress hormone cortisol, according to a 2011 study published in Developmental Psychology. Not only that, people in the study didnt feel as upset about the experience if their best friend was around (meaning that post-breakup sleepover is totally backed by science).
2. Being there for them cheers you up too.
Showing up at a friends house with their favorite latte after they had a killer week at work or sending them a card when theyve been under the weather makes you both feel better. A 2010 study published in the Journal of Happiness Studies found that feeling important to or relied on by close friends was a big reason why friendships made people happy.
3. They talk to you about the real stuff.
Discussing the amazingness of Katy Perrys Left Shark is part of what friends are for. But its the big deal things you discuss (cross-country moves, career changes) that really make a difference. Having those substantive conversations contributes to your overall well-being, according to a 2010 study published in Psychological Science.
4. It's not just BFFseven casual friends boost your mood.
That coworker you trade book recommendations with or the woman you chat to while setting up your bikes in spin class might not count as close friends, but they still brighten your day. Interacting with more peopleeven casual acquaintancesgives people a sense of belonging and makes them feel happier, a 2014 study published in the Personality and Social Psychology Bulletin found.
5. Their good days are contagious.
If your pal just got a promotion or booked her dream trip to Machu Picchu, make a date to hang out. When your friends in a good mood, itll put you in a better mood too. A 2008 study published in the British Medical Journal found that people were 15 percent more likely to be happy themselves when they spent time with a happy friendand that feel-good effect stretches all the way to their friends' friends' friends.
6. The good feeling of a friendship lastsand lasts.
The OMG-my-life-is-amazing effect of exciting milestones, like buying a house, can wear off after a while (psychologists call this hedonic adaptation). But our relationships seem to be an exception to that rule, according to a 2011 chapter published in the Oxford Handbook of Stress, Health, and Coping. Your friends continually give you new reasons to be happy over timeso keep scheduling those margarita happy hours.