As my mother was getting her weekend grandchild fix over the phone last Sunday, I knew she'd be asking about the new school year and how each girl was getting along. The phone was passed from one person to the next. And then, in answer to some question my mom had asked, I overheard my daughter say quietly, evenly: "I don't have a friend yet."

My ears pricked up, but mere murmuring followed. We were two weeks into a new school experience for this child and her older sister; I'd been trying to play it cool and not ask too many questions about how they were feeling, despite my desire for assurance. It was too early for the kids to have made a fair assessment that would please me, and we've been through school transitions before. Indications thus far were that I didn't need to worry too much.

But now, from the child who is the most happy-go-lucky of the brood, a reminder that much work remains to be done on feeling copacetic.

Back to "playing it cool." As I prepared dinner that evening, I limited myself to one question when my daughter came into the kitchen. I gently repeated what I'd heard: "J.J., did you tell Grandma that you didn't have a friend at school?"

And from her answer, I quickly realized the value of the BFF.

It's not that this child has trouble making friends. What my daughter meant is that she has yet to find that extra-special connection which binds two people and shields you like a pillow against the hard edges in life. She's been lucky to have found those counterparts in her other schools, and fully expected to have identified the potential among her new peers by now.

I've met many of the parents in J.J.'s class (it's a small group), with their warm and welcoming attitude, and I'm sure their kids are not unlike them. As a whole, I'm pretty certain they are a lovely bunch. But, being able to identify oneself as a unit with another individual is distinct from being part of a nice group. The "forever" part of BFF aside, having a best friend, or a couple of them, makes all the difference.

Unlike the rules for what science tells us you should put into your body – recipes for a healthy diet continue to evolve – the evidence for how good friendships are for your health continues to grow. In adulthood, having friends is linked to longer life and a lowered risk of some diseases (though there's some evidence linking obesity to your social ties). Some researchers believe that knowledge of your friends' happiness, and even their friends' happiness, has a positive effect on yours.

The friendship dividend is even richer for females. For women, who experience friendship differently than men (an understatement, you might say), friends can facilitate stress reduction. Using magnetic resonance imaging (MRI), researchers have begun to see how teenage girls differ from boys in social interactions. Girls' brains show increased activity when faced with one-on-one interaction, while boys brains do not. In general, boys are more concerned with groups and competition and their place in the pecking order, not individual relationships.

And early this year, a study of elementary schoolchildren was published that documented a significant number of misunderstood relationships: Sometimes, you think someone is your friend – while he, or she – says he isn't. Kids considered more socially skilled were sometimes named as a friend by a child they disliked. Conversely, those who had more trouble getting along with others were often disliked but unaware of it.

Science, schmi-ence, you say. As a healthy, social being, my daughter already realizes how important friends are. Parents and teachers have recognized the value of friendships long before they had to invent the word "play date." But it does affirm all the effort we've expended since the days when we invited all our Before-Kids friends (and their babies) to the firstborn's one-year-old birthday party.

In the past few days, in our conversations I've slipped in some talk about how we can appreciate different kinds of friends. For example, the moms of J.J.'s best friends are not necessarily my BFs. Sure, we love those olympic rings of family friendship, when there's an ideal gold medal combination of all the kids and spouses who get along and enjoy being linked together. But not all friends need to be the kind you could share a beach house with. And while a child may not find the relationship she yearns for right away, the resilience required to seek out those special new ties will help her cherish the old ones even more.

We'd like to share some stories from families with boys in this space. If you would like to write about yours or tell me a tale, send the author an e-mail.