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.
Family and Social Environment
For some teens, a negative, stressful, or unhappy family atmosphere can affect their self-esteem and lead to depression. This can also include high-stress living situations such as poverty; homelessness; and violence in the family, relationships, or community.
Substance use and abuse also 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 also can lead to severe unhappiness and depression.
Medical Conditions
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.
For some teens, undiagnosed learning disabilities might block school success, hormonal changes might affect mood, or physical illness might present challenges or setbacks.
