Depression is a mental illness marked by feelings of profound sadness and lack of interest in activities. It is a persistent low mood that interferes with the ability to function and appreciate things in life. It may cause a wide range of symptoms, both physical and emotional. It can last for weeks, months, or years. People with depression rarely recover without treatment.

The exact cause of depression is not known. It may be due to a certain type of brain chemistry. While the exact cause is not clearly established, factors that may play a role in depression include:

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