Why Do People Get Depressed?

There is no single cause for depression. Many factors play a role including genetics, environment, medical conditions, 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 self-esteem and lead to depression.
Social conditions like poverty, homelessness, and community violence can make it more likely for people to become depressed.
For some teens, undiagnosed learning disabilities may block school success, hormonal changes may affect mood, or physical illness may present challenges or setbacks. With or without the genetics for depression, any of these can set the stage for depression.
Substance abuse can cause chemical changes in the brain that affect mood - alcohol and some drugs are known to have depressant effects. The negative social and personal consequences of substance abuse can also lead to severe unhappiness and depression.
Certain medical conditions can affect hormone balance and therefore have an effect on mood. Some conditions, such as hypothyroidism, are known to cause a depressed mood in some people. When these medical conditions are diagnosed and treated by a doctor, the depression usually disappears.