Sadness is one of the cardinal negative emotions. While every human being has experienced sadness, the intensity of their experiences can vary dramatically. Like all emotions, sadness has an evolutionary advantage that has resulted in it being preserved as an essential part of being human.The greatest cause of sadness is loss. The classic example is the loss of a significant relationship. When we lose a loved one, we describe the intense sadness as grief. We know that grief is universal and that grief plays an important role in helping us to mourn the loss of someone we have loved.While the negative impact of depression has an enormous public health consequence, the good news that has evolved over the past two decades is that our treatments for depression are increasingly effective. Given the fact that many depressed individuals fail to seek treatment, reaching out to people who are depressed and would have a high likelihood of responding to treatment should be a major health priority.