I am not sure about the answer to that, but speaking of mood, I can tell you about Bipolar disorder, which causes people to have periods of depression as well as periods with the mood elevated. Have you ever heard of it ?
Sounds like it could be Bipolar disorder. :(
How can you explain people can change emotional behaviors all of a sudden?
Bipolar disorder, previously known as manic depression, is a mental disorder that causes periods of depression and periods of elevated mood.