For the past three years, I have had the pleasure of teaching the course “Psychology of Relationships” to eager students yearning to learn about the nature of human relationships, and hopeful to glean some scientific insight into how to improve their own.

What I have found that my students enjoy learning most, perhaps given the current climate of casual relationships which can go ill-defined, are the key factors which make an intimate relationship namely that — intimate. What a common misconception around ‘intimate relationships’ is, however, is that they are only within the domain of romantic or sexual relationships. Indeed, perhaps our most intimate relationships needn’t require sex or romance, but simple friendship. Interestingly enough, it’s of no surprise then, that the commonalities between romantic and best friendships often cross-over.

According to researchers Ben-Ari and Lavee, the happiest intimate relationships are often different than other characteristic relationships in seven distinct ways. In other words, these are what make our best friendship ‘work’:

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When forming deep, intimate relationships, we share a vast amount of personal information that we wouldn’t necessarily feel comfortable sharing with others. Of course, the amount of information may differ from one person to the next; research shows that women, on average, tend to share more intimate information with their friends as well as partners, in comparison to men, who generally reserve more intimate topics for their partners. Nonetheless, with our close friends, when in healthy relationships, we feel safe sharing our deepest dreams, desires, fears, past histories, traumas and goals for the future. Generally, this is a reciprocal and gradual process.

Interdependence

Our deepest friendships also tend to be highly interdependent, wherein each friend influences the other meaningfully, frequently, and vastly, in terms of topic and importance. This can range from choosing what to eat for dinner to where to live. Often, this is why we take our friend’s advice to heart. They influence us, and we have trust that they are doing so with our best wishes in mind.

Care

Care is another hallmark of healthy close friendships. There is a considerable amount of care each friend places in the other, and this differs from the care that one would typically display to another, non-intimate person. Friends thus show concern for each other’s well-being, comfort in times of distress, and safekeeping the other from harm. While the display of care can differ from one person to the next (as a function of communication style or differing displays of affection, for instance), close friends tend to display genuine, selfless care for each other.

Trust

In my opinion, trust is what holds the other six components of intimacy together. Trust is a difficult concept to discuss because of its complexity, but we certainly feel it even without fully being able to define it. In my estimation, trust is the confidence that we place in another human being to act in a way of honor and fairness that is of benefit to us, or at the very least, that our friend or indeed romantic partner will not cause us purposeful harm.

Responsiveness

Healthy close friendships involve people who are mutually responsive to each other’s needs. This means recognizing, understanding and supporting each other, both in times of pain (e.g., losing a parent or a job) and gain (e.g., getting a promotion, announcing a pregnancy). When each friend feels like the other meets his or her needs, this culminates in feeling appreciated, connected and loved.

Mutuality

Though this is more true in romantic intimate relationships, friendships do involve a certain sense of mutuality, as well. For instance, after a certain point within a healthy friendship, each friend recognizes a close connection to the other. No longer does one person feel alone and solitary in the world, but a close friendship changes one’s sense from being a ‘me’ to a ‘we’. What am I doing becomes ‘what is my friend group doing this weekend’, or the oft-used “girls” or “boys” night. Before a friendship forms in a solid way, for instance, one might consider their weekend plans as “what am I doing this weekend” but after forming a deep friendship, one might consider “what are my friends, what are ‘we’ doing this weekend?” e concept of mutuality helps us to feel secure in the world, and thus is no surprise that it reforms of psyche from seeing ourselves as ‘me’ to a ‘we’.

Commitment

Lastly, within healthy friendships, there is little guess work involved: there is a mutual volition for wanting the relationship to continue indefinitely, which further allows the other six components of intimacy to grow. With the idea that the friendship is to continue for an indeterminate amount of time, it allows for trust to continue to deepen, common knowledge to further be shared, mutuality to envelop, care to be shown, and continual effort be put into responsiveness and interdependence for both partners.

While these are the components that characterize healthy mutual friendships as intimate or close, violations of these characteristics can certainly be the reason why friendships end, even when we don’t understand why they must.

When friendships end, it’s no surprise then that it can be as heartbreaking as a romantic relationship, because you are losing all of these components and a truly intimate relationship. To give a very personal example, when I was 22, a very close friend of mine who I’d imagined to become a lifelong friend, had betrayed me in a way I couldn’t fully understand. It violated so much of what I’d known of her for the years we’d been close friends and the memories we’d shared. The basic details of the example include that she had taken an idea that we had jointly created and ventured out on her own, taking full ownership of it, without fully telling me until it was too late. It was something that hurt me deeply and I spent much time trying to understand why I felt the friendship could no longer continue. If only I had known about the seven components of intimate relationships, it would have been helpful to understand. When we feel violated by even one of these components, it can seep into how we view that relationship, and certainly cause cracks in the other components, as well.

In my case, my friend had violated our mutuality. No longer were we a ‘we’ about to embark on a new adventure together, but all of a sudden, ‘we’ had become a ‘she’. This immediately violated the trust I had in her—if she had decided on this route alone, could I trust that in the future, she wouldn’t do the same thing?

From there, I stopped speaking to her as much as I normally would, thus dampening the knowledge I shared with her and the feelings of interdependence. Her responsiveness to me changed, as did mine to her, and with that, the care we felt about each other. Perhaps the hardest to overcome was the commitment we had in each other. Having been childhood friends, our friendship was characterized by not only memory after memory of growing up together, but the many plans of the future that we had—attending each other’s eventual weddings, having our children play together. Once one crack had occurred in the seven components, however, the rest shattered, resulting in a very painful disconnect from a once-trusted good friend.

At the end of the day, when it comes to evaluating the making and breaking of friendships, perhaps the best way to consider your friendships and your happiness within them is to ask yourself what I believe to be the basis of these seven components: does this friend want the best for me? And secondly, do I want genuinely what’s best for them? If the answer is an honest ‘yes’, then do your best to adhere as closely to the seven components as possible, and trust yourself to be a good friend.