Learned Helplessness
When an organism (person, animal, etc.) is prevented from avoiding some aversive stimulus repeatedly (e.g., continuous electric shocks) the organism will reach a state in which it becomes passive and depressed because he believes that there are no actions it can take to avoid the aversive stimulus. Esssentially, the organism just gives up trying to avoid it and just takes the aversive stimulus. Thus, the organism learns that it is helpless against the aversive stimulus.