If you have a mood disorder, your general emotional state or mood is distorted or inconsistent with your circumstances and interferes with your ability to function. You may be extremely sad, empty or irritable (depressed), or you may have periods of depression alternating with being excessively happy (mania).
Anxiety disorders can also affect your mood and often occur along with depression. Mood disorders may increase your risk of suicide.
Information above from MayoClinic.org (Click here to read more)