This piece is taken from Healthy at 100: How You can At any Age-Dramatically Increase Your Life Span and Your Health Span by John Robbins  

There is an aspect of our lives that healthy traditional cultures have always understood to be of paramount importance to human happiness, well-being, and longevity: Nothing is more important, they believe, than the quality of their human relationships. As individuals and as communities they are sustained through all kinds of hardships by the boundless commitment they have to support one another, and their complete readiness to provide mutual aid at any time.

If you happen to leave your wallet on the sidewalk in Okinawa, you can fully expect to come back the next day and find it still there .It if it’s gone, it’s probably only because some anonymous stranger who picked it up will soon return it to you, completely intact. 

Similarly, in Abkhasia, people are valued over anything else. Wealth is counted not by the amount of money a person has, but by the number and quality of relationships he or she maintains. In Abkhasia, people are said to be successful as a result of having a large bank account, much land, or many possessions. Instead, people are considered successful if they have a large and vibrant network of loyal and devoted people in their home, extended family, and community. 

In Vilcabamba, Equador and in the Hunza Valley in Pakistan too, the sense of connectedness people have with one another and the way they relate to each other are held to be of primary significance. Generosity and sharing are the highest values. Nothing is more important than how people treat each other.

Thirty years ago, anyone who said there were profound medical consequences to human relationships would have had their sanity questioned by modern science. And anyone blaming loneliness for physical illness would have been laughed at. But in the last few decades there has been an explosion of scientific understanding about the deep connections between interpersonal relationships and health.

As you may know, there is in Western medicine a great deal of concern about risk factors like high blood pressure, high cholesterol, smoking and obesity-and deservedly so, for they are very often linked to serious disease. But an ever-increasing body of medical research is coming to the surprising conclusion that the quality of your relationships with other people is every bit as important to your health as these indicators-if not more so. Chronic loneliness now ranks as one of the most lethal risk factors determining who will die prematurely in modern industrialize nations. 

Though the science has been accumulating for the last thirty years, many physicians have been slow to accept the idea that something as intangible as interpersonal relationships could have so much medical significance. They tend to view love as a frill or a luxury, as something that distracts from a rational approach to patient care. 

It is a sad statement about modern medicine that so many physicians consider it to be their professional obligation to remain emotionally distant from their patients when in fact the healing power of love and relationship has been documented in an ever-increasing number of well-designed scientific studies involving hundreds of thousands of people throughout the world. 

Modern research is now repeatedly finding that your relationship with others is medically potent. Your connections with significant people in your life-if they are positive and loving-can prevent stress-induced illness, greatly contributes to your health and healing and add many years to your life. An abundance of positive, meaningful relationships is one of the secrets of the world’s healthiest and most long-lived peoples.”