This one thing could help the mental health crisis among teen girls.

Friendship.

This might surprise you. You might think the source of your child’s anxiety is school or Instagram or body-image issues, and all of this could be the case, but when a teenage girl has a close friend or two whom she can confide in about these issues, she is much better off than a teen girl who is isolated from her peers. And having a lot of Instagram followers does not mean she has friends.

Research proves that girls don’t need a lot of friends to attain the mental health benefits of friendship. In fact, having fewer but deeper friendships could be key. New research published in the mental health journal Child Development shows that teens aged 15 and 16 who had one close friend, rather than a bigger peer group featuring less intense relationships, reported higher levels of self-worth and lower levels of social anxiety and depression at age 25 when compared with their peers who were more broadly popular as teens.

Another study confirmed that when a girl was affiliated with a broader group of friends, she was more likely to suffer from anxiety. The authors concluded that girls who prioritize forming close friendships are better able to manage social and developmental tasks as they move into adulthood than girls who try to fit into a large social group.

This is an important point for parents. We often preach to our daughters that they need to expand their group of friends or get involved in more activities. We do this because we want our daughters to be popular and well-accepted. What we fail to realize, however, is that having a large group of friends is stressful for some girls and can make them more vulnerable to peer pressure and bullying. Having a few good friends can be much better for a girl than having more friends who are less close, and perhaps less kind and less supportive.

It’s quality over quantity when it comes to our girls and their friends, and as an adult you know, not all friends are good for our kids. This is where your involvement in your daughter’s life is critical. You can help point out the quality friends over the drama queens, mean girls, and friends that you can tell are simply sucking the life out of your daughter.

The best way you can help your daughter form healthy friendships with the right friends is to stay closely connected to her. This means being invested in her life, but not hovering over her. It’s a balancing act that mothers in particular can find difficult. All too often, mothers try to remain “close” to their daughters by joining them in their friendships, and girls don’t like this. It is appropriate and helpful to become friendly with your daughter’s friends—as long as you remember that you are a parent, not a peer. So, don’t friend your daughter’s friends on Facebook. Your friends should be adults; hers should be her peers.

By maintaining an appropriate distance, you increase your authority—you are, after all, the adult. And you are in a great position to advise your daughter simply by listening and asking gentle questions that direct her to figure things out for herself as far as which friends are healthy and which ones are not.

Our daughters need good and loyal friends. We know this as parents and scientific research proves it. As parents, we can help guard our daughters against the mental health crisis they are facing by helping them recognize and pursue true friendship—the sort of friendships that can transform their lives forever.