Stress relief. When things get crazy, you might feel far too busy to schedule that brunch. But when you’re slammed, that’s actually when you need your friends the most: the laughter, distraction, and catharsis that they can provide are among the best medicine there is. And they work wonders for bringing down your blood pressure, clearing your mind, and helping you sleep better. (It’s not just the mimosas!)

Countering Depression. You might have enough Facebook “friends” to fill a concert hall but still feel a profound sense of isolation. Close, nourishing relationships, however–those of the genuine kind–provide meaning and support that research has shown can help ward off depressive thoughts and behaviors, and help you recover more quickly if you do succumb. What’s at stake? Depression’s effects are not just mental: it’s been implicated in everything from heart disease to chronic pain.

Setting the Example. When you’re good friends with healthy people, you tend to reap immense benefits. That means everything from wearing sunscreen and quitting those cigarettes to being more patient and optimistic is directly affected by the people you choose to spend your time with. Subconsciously and consciously, healthy friends make you want to be a healthier you.

Sounding The Alarm. Not only are your friends role models, but they also serve as fire alarms to alert you to problems with your current health. Many times, it’s your friends who are on your case first, whether you’re hitting the martini bar a bit too much or you’re running yourself ragged at the office. One of our friends’ most important roles is to help us know–and intervene–when we slip into patterns that aren’t good for us.

Overcoming Trauma. In an ideal world, none of us would ever experience something horrific. But trauma happens somewhere, every day of the year: from assaults to car accidents to natural disasters. Amazingly, social support can make a big difference in helping someone recover. In fact, the more solid your friendships are, the smoother your recovery–and the less likely you are to develop Post-Traumatic Stress Disorder, a potentially debilitating condition.