Joseph Allen, a psychologist at the University of Virginia, and his colleagues have been studying for decades the teen brain. In particular, he has been focusing on the impact of teen relationships and stress on adult romantic relationships.

Here’s what they’ve discovered in their latest research:

Having a best friend teaches you intimacy

Young teens – 13, 14 years old – often have close relationships with same-sex best friends, friendships that often continue through the teen years and beyond. While some parents overreact to these relationships – Is my son/daughter gay? – what these relationships provide, unlike early romantic/sexual relationships that are often unstable, are something important – a foundation for learning about intimacy, opportunities for being assertive and learning how to handle differences – all-important relationship skills. Having and sustaining these best-friend relationships in the teen years, the research shows, are a good predictor of successful adult romantic relationships.