Objective: To discuss the psychological pathogenic factors for and pathological mechanisms of depression and mania. Methods: Case analysis, simulated experience, and theoretical idea. Result or Conclusion: The psychological pathogenic factors for depression and mania are all of an emotional breakage between a person and the interpersonal world, which is caused by an individual separating him/herself emotionally from the interpersonal world. There are many causes of the occurrence of such a situation, yet the person still yearns to integrate emotionally into the interpersonal world. The continuance of this psychological conflict will make a person’s psychological energy drained, and cause him/her to emotionally forgo the interpersonal world at last. Thereafter, depression will occur if his/her interest and psychological energy are directed towards the self; and mania will occur if towards the image associated with wish, desire, sentiment and emotion.