Sadness and grief are normal human emotions. We all have them at some point in our lives, but they usually go away within a few days. However, major depression, also known as major depressive disorder, can last longer. It is a diagnosable condition, classified as a mental disorder, and can cause long-lasting symptoms such as sadness, low energy, loss of appetite, and loss of interest in things that used to bring us joy.

Depression can become a serious problem if left untreated. Untreated depression increases the risk of dangerous behaviors such as drug or alcohol abuse. Untreated depression can also ruin relationships, cause problems at work, and make it difficult to cope with serious illnesses.