Sometimes we feel tired from working hard, or discouraged when faced with serious problems. This too, is not depression. These feelings usually pass within a few days or weeks. But, if these feelings linger and begin to interfere with work, school or family responsibilities, it may be depression.

There is no single cause for depression. Many factors play a role including genetics, environment, life events, and certain thinking patterns that affect a person's reaction to events.

Research has revealed that depression runs in families and suggests that some people inherit genes that make it more likely for them to get depressed. But not everyone who has the genetic makeup for depression actually gets depression. And many people who have no family history of depression have the condition. So, although genes are one factor, they aren't the single cause of depression.

Life events - for example, the death of a close family member or friend - can go beyond normal grief and can sometimes lead to depression.

Family and social environment also play a role. For some teens, a negative, stressful, or unhappy family atmosphere can affect their life and lead to depression.

Social conditions like poverty, homelessness, and community violence can make it more likely for people to become depressed.

We have to say that People who are depressed shouldn't wait and hope it will go away on its own, because depression can be effectively treated. Although depression is one of the most common emotional problems, the good news is that it's also one of the most treatable conditions.