What is major depressive disorder?

It is a serious medical illness that disrupt a person; mood, behavior, thought process and physical health.

It is characterized by a persistent lowering of mood, loss of interest in usual activities and diminished ability to experience pleasure.

Major depressive disorder is a recurrent, episodic illness. This means that a person who has been depressed once and has recovered is likely to have one or more episodes of depression in future, often within 2 to 3 years.

Major depressive disorder has about a 50% chance of developing another episode at some later point. Once individual has two episodes, the odds of having a third increase to about 70%.

An episode of major depressive disorder may be classified as:
*mild
*moderate
*severe

Major depressive disorder may be accompanied by hallucination or delusions: these may be congruent or non congruent with the depressive mood.

Major depressive disorder can present with a variety of symptoms, however almost all patients display a marked change in mood, a deep feeling of sadness, and noticeable activities.
What is major depressive disorder?