 Sadness is also distressing, yet is widely believed to be an evolved adaptation.In fact, perhaps the most influential evolutionary view is that most cases of depression are simply particularly intense cases of sadness in response to adversity, such as the loss of a loved one.According to the psychic pain hypothesis, depression is analogous to physical pain in that it informs the sufferer that current circumstances, such as the loss of a friend, are imposing a threat to biological fitness.