Some people are more moody than other people. Normal mood actually varies from person to person. That’s because we all have different “temperaments,” or combinations of personality traits that are biologically based. These are fairly stable over time.
Considerable research shows that people really differ in their basic temperament. There are some people who temperamentally are always in a “good” mood. And there are people who are temperamentally always in a “bad” mood. People who have a more negative temperament tend to have a higher risk for mood and anxiety disorders.