Many people deal with problems in life in many different ways.  It is better to see the causes of depression in perspective if you understand that there is a wide spectrum of human reaction to any given set of circumstances.  One person may have a breakdown as a result of a bereavement or divorce, another will find unexpected strength, and cope calmly and efficiently with the crisis and its emotional effects.  This is not to say that the individual is not suffering, rather that she would go into a grief phrase and suffer, but emerge from it after an average time interval as stable and maybe stronger than before.  On the other hand, another person, by contrast, may never have suffered a personal tragedy in his life, but may be severely affected by depressive illness arising for no identifiable reason.