The disorders in this category include those where the primary symptom is a disturbance in mood - In other words, inappropriate, exaggerated, or limited range of feelings. Everybody gets down sometimes, and everybody experiences a sense of excitement and emotional pleasure. To be diagnosed with a mood disorder, your feelings must be to the extreme. In other words, crying, and/or feeling depressed, suicidal frequently. Or, the opposite extreme, having excessive energy where sleep is not needed for days at a time and during this time the decision making process in significantly hindered.
Researchers believe most serious mental illnesses are caused by complex imbalances in the brain's chemical activity. They also believe environmental factors can play a part in triggering, or cushioning against, the onset of mental illness.
Like other diseases, mental illnesses can be treated. The good news is that most people who have mental illnesses, even serious ones, can lead productive lives with proper treatment. Mood disorders are one form of serious mental illness.