'Clinical depression': What does that mean? Depression ranges in seriousness from mild, temporary episodes of sadness to severe, persistent depression. Doctors use the term "clinical depression" to describe the more severe, persistent form of depression also known as "major depression" or "major depressive disorder." Signs and symptoms of clinical depression may include:
-Loss of interest in daily activities
-Persistent sadness or feeling of emptiness
-Sleep disturbances
-Significant weight loss or gain
-Loss of concentration
-Fatigue
-Suicidal thoughts or behavior
