According to his work and that of others, the degree of pain is not a reliable indicator of the severity of injury. And sometimes there is pain without any tissue damage at all.

An extreme example came from a 1995 report in the British Medical Journal. A builder jumped onto a nearly six-inch nail, which penetrated his boot’s sole, the tip visibly protruding from its top. To relieve his excruciating pain, doctors administered fentanyl and a sedative. But, when they removed the boot, the doctors discovered that the nail had passed between his toes, leaving his foot unharmed. There are many studies that find that the fear or catastrophizing of pain contributes to a greater feeling of pain.

When our brain decides to interpret a sensation as painful, it also sends a signal back to the body that intensifies that feeling. Nerve endings can chemically change in response to signals from the brain. Pain is more like a conversation between the brain and the body. And like verbal conversations, it can be heated or calm.

If something in the mind — fear — can make pain worse, can some other thoughts or mood make it better? Yes, to an extent.

For example, pain can be lessened when we feel safe. An early demonstration of this fact came from a study in JAMA in 1956. In it, wounded World War II soldiers were compared with civilians with similar injuries. Though 83 percent of the civilians requested narcotic pain killers, only 32 percent of the soldiers did. One interpretation of these results is that the soldiers felt safer just being off the battlefield, and that the relative sense of safety diminished their feeling of pain.

I experienced something akin to this when I had a kidney stone. Its pain was excruciating at home as well as on the way to the emergency department. But once there, I felt safer, and the pain began to subside even before I was given painkillers.

Love, like safety, can also ease pain. For example, a study published in Pain Medicine found that people who spend a greater portion of their day thinking about a romantic partner experience more pain reduction when viewing pictures of that partner than those less preoccupied with their partner. Other studies show that pain is reduced when partners hold hands.