What is depression?

The word depressed is a common everyday word. 
People might say "I'm depressed" when in fact they mean "I'm fed up because I've had a row, or failed an exam, or lost my job", etc. 
These ups and downs of life are common and normal. Most people recover quite quickly. 
With true depression, you have a low mood and other symptoms each day for at least two weeks. 
Symptoms can also become severe enough to interfere with normal day-to-day activities.