Having a family member go missing is called "ambiguous loss". It is one of the most painful types of loss because there is no possibility of closure or resolution. With no official proof of loved ones being dead or alive, relatives and friends of the missing flight MH370 suffer the agony of not knowing. Unlike with certain death, there is no official verification, no funeral or rituals of support, and no finality. People understandably maintain hope. And sometimes, just enough times to keep hope alive, a missing person does come walking out of the jungle or a kidnapped child is found alive.

The families and friends of the missing are stuck in a painful limbo where relationships are brutally ruptured and yet grief is frozen. While those who wait for news may exhibit symptoms of depression, anxiety and anger, we must remember that the source of pathology lies in their irrational situation of loss. The ambiguity is the culprit. Oscillating between hope and despair, families understandably resist change because they still hope to find the missing person. Our task is to have patience with their suffering and learn to hold the ambiguity with them.

After decades of studying families of the missing, I find that people accustomed to finding answers and solving problems may suffer more because they insist on closure. For example, many New Yorkers were stunned and some even angry just weeks after 9/11 when families of the missing continued to hope that their loved ones would turn up alive somewhere. (A few actually did.) One year later, a New York reporter doing a story on the anniversary of 9/11 asked me why I thought New Yorkers weren't over it yet. My answer: "Because you're trying to get over it."

Paradoxically, as TS Eliot suggests, what we do not know about a missing loved one becomes all that we know. Another poet, John Keats, recommends in his letters to a young poet that he develop a capability for living with unanswered questions. Keats called this "negative capability" – and this is what it takes to live with loved ones gone missing. This is also the way for the rest of us to stop pressuring these families to find closure.

In cases of ambiguous loss, meaning will not emerge from absolute thinking. Rather, it comes from our being able to hold two opposing ideas at the same time (I think of F Scott Fitzgerald). Such paradoxical thinking requires a cognitive shift toward multiple meanings – the only way one can survive with ambiguous loss. Decades after her boy was kidnapped, a mother told me: "He's probably dead ... but maybe not. I still hope to see him once before I die." She has found the capability for living with what remains a mystery, as the families of passengers on flight MH370 may also have to.

The ability to hold two conflicting ideas in one's mind at the same time provides the resilience to move forward even while the ambiguity persists. Given the absurdity of ambiguous loss, human strength emerges not from one absolute truth, but from holding on to an array of possibilities.