Why Do People Get Depressed?

There is no single cause for depression. Many factors play a role including genetics, environment, life events, medical conditions, and the way people react to things that happen in their lives.
Genetics:
Research shows that depression runs in families and that some people inherit genes that make it more likely for them to get depressed. Not everyone who has the genetic makeup for depression gets depressed, though. 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:
The death of a family member, friend, or pet can go beyond normal grief and sometimes lead to depression. Other difficult life events, such as when parents divorce, separate, or remarry, can trigger depression. Even events like moving or changing schools can be emotionally challenging enough that a person becomes depressed.