What Is Major Depression? - Definition, Symptoms & Causes

Instructor: Yolanda Williams

Yolanda has taught college Psychology and Ethics, and has a doctorate of philosophy in counselor education and supervision.

Did you know that depression affects an estimated five to eight percent of the U.S. population? Learn more about major depression, its symptoms, and causes. Then test your knowledge with a quiz.


We've all had feelings of sadness from time to time. Maybe you saw something on television that made you feel down. Or maybe you have been let down by a friend and it made you sad. Despite these feelings, you were still able to function normally for the most part, and eventually you were able to get back to being your old self. For individuals who suffer from major depression, things are different. They may not be able to get back to feeling 'normal.' The depression influences every aspect of their lives, including their thoughts, behaviors, and feelings.

Major depression is a mental disorder that is characterized by persistent feelings of sadness, loss, or anger that last for most of the day and a decreased interest or pleasure in most activities. Major depression is classified as a mood disorder, which refers to psychological disorders that are characterized by persistent elevation or lowering of a person's emotional state or mood. The symptoms of major depression can last for weeks or longer. While some people only have one episode of depression, it's more common for people to have recurrent episodes over their lifetime.

Depression is linked to an increased rate of heart disease, stroke, and diabetes. It is estimated that between five and eight percent of Americans suffer from depression, and this percentage is expected to increase significantly in the coming years. There are several theories as to what is causing this increase, including lifestyle factors, such as poor diet and sedentary lifestyle; sleep deprivation; modern society being more competitive, lonely, and self-focused; and economic disparities.

Even worse, research indicates that 80% of individuals who have symptoms of major depression are not currently being treated. Major depression is also known as major depressive disorder (MDD) and clinical depression.


The Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) is a handbook that lists the requirements to diagnose a specific mental disorder. It lists the following symptoms of major depression:

  1. Depressed mood or irritability that lasts most of the day, every day
  2. Decreased interest or pleasure in most activities that lasts most of each day
  3. Significant weight loss or weight gain, as indicated by a five percent change in weight
  4. Sleeping problems (either too much or too little)
  5. Change in motor activity
  6. Fatigue or lack of energy
  7. Persistent feelings of worthlessness or inappropriate guilt
  8. Trouble concentrating
  9. Recurrent suicidal thoughts or behavior

In order to receive a diagnosis of major depression, a person must exhibit at least 5 of the 9 symptoms listed above during the same 2-week period. At least one of the symptoms must be depressed mood or decreased interest or pleasure. Other symptoms of depression include:

  • Feelings of hopelessness or self-hate
  • Withdrawal from social settings and events
  • Reduced sex drive

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