"A mental disorder characterized by a consistent, pervasive alteration in mood, and affecting thoughts, emotions, and behaviors"

The American Heritage® Dictionary of the English Language, Fourth Edition, 2000, Updated in 2009. Published by Houghton Mifflin Company.

"Mental disorder characterized by dramatic changes or extremes of mood. Affective disorders may include manic (elevated, expansive, or irritable mood with hyperactivity, pressured speech, and inflated self-esteem) or depressive (dejected mood with disinterest in life, sleep disturbance, agitation, and feelings of worthlessness or guilt) episodes, and often combinations of the two. Persons with an affective disorder may or may not have psychotic symptoms such as delusions, hallucinations, or other loss of contact with reality."

Source: Encyclopaedia Britannica

Thank you, I found this definition as well. But it doesn't say anything about anxiety or anxiety disorders. Therefore, I am not sure if anxiety disorders can be put under this category...

Dear Susan, thank you for the references!