The simple truth is that we don’t really know. One reason, though, is that there are fewer distractions at night. During the day, we need to concentrate on many things besides our pain. Phone calls, business meetings, and errands actually serve as powerful non-drug painkillers, because when our mind is preoccupied with other things, it feels less pain. At night, the diversions and stimulation around us drop, leaving plenty of time for the brain to focus on our discomfort. This phenomenon was noticed in American armed forces at Anzio Beach during World War II. When severely wounded soldiers were evacuated from the front lines they didn’t react to pain in typical ways. Why not? The relief of being removed from danger was so great that it distracted them from their suffering. Talk to your doctor about the possibility of a low-dose nighttime painkiller or a non-addictive sleep aid.