Answer to Question 1
A person with a major depressive disorder has at least one major depressive episode that lasts 2 weeks or more during which there is either depressed mood or the loss of interest or pleasure in nearly all activities (American Psychiatric Association, 2000). Almost everybody experiences occasional episodes of mild depression or the blues. However, a person with a major depressive episode experiences depressed moods that stretch throughout the day almost every day for at least 2 weeks. Besides depressed mood or loss of interest in pleasurable activities, symptoms of this form of clinical depression include most, but not necessarily all, of the following: almost daily insomnia or hypersomnia (sleeping too much), significant weight loss (not due to dieting) or gain, excessive daily fatigue, feelings of worthlessness or inappropriate guilt, poor concentration, or recurrent suicidal thoughts. As you can see, this is significantly more severe than the blues.
Answer to Question 2
There is a large body of social psychology research showing that catharsis activity is not only ineffective in reducing anger, but it actually increases rather than decreases hostility and aggression (see Aronson, Wison, & Akert, 2010, pp. 374-378, for a discussion). For example, Aronson et al. (2010, p. 375) note that verbal acts of aggression are followed by further attacks.. The reason catharsis does not work is because it hardens thoughts and attitudes that foster blame and derogation of the target of anger. This then leads to self-justification for harboring angry feelings. Such self-justification can lead to acting on the angry feelings in an aggressive way. The unintended effect of catharsis is to add more steam to the steam engine, causing it to overheat and go off the tracks.