is a feeling that everyone gets from time to time, but when it gets excessive, can cause serious problems in a person's life.
is a problem with persistent sadness so severe that it can also cause physical problems (e.g. problems with sleep, concentration, energy, appetite) as well as problems with home, school, work and relationships.
is when you are in a relationship, and the other person abuses or controls you physically or emotionally.
play a key role in mental health and happiness, and the most important relationship is your relationship with your spouse / partner.