When you're talking about a mood disorder, you may be just trying to classify 1 of the 3 major areas of psychiatric disorders. Psychiatric disorders can basically be broken up into psychotic disorders, anxiety disorders, and mood disorders. Mood disorders refers to the group of disorders where, as the name implies, the main problem is with an individual's mood. And there's basically 2 categories of mood disorders. There's the depressive disorders, in which the main symptoms have to do with depression, which I'll talk a little bit about. And then the other grouping is with bipolar disorders. The main example of that is bipolar 1 disorder. But there are several types of bipolar disorders. And what differentiates the 2 kinds of mood disorders, is, depressive disorders involve only disturbances of low mood or depression. Whereas, bipolar disorders have periods of depression, but they also have periods of elevated mood, or mania, or hypmania, and things like that. The main issue to understand about mood disorders, is that, as I said before, they involve a disturbance in an individual's mood, the way that they feel. The interesting thing is that individuals may not always be aware that they're having disturbances of mood. And this is the reason that people often don't come to treatment. So basically, when talking about mood disorders, it differentiates from anxiety disorders, on 1 hand, and psychotic disorders on the other, where the main disturbance is an issue of low, or in some cases, low and elevated mood. And that's a basic definition of a mood disorder.