Everyone feels sad from time to time. But depression is much more serious than just feeling down. Depression is a real illness, just like diabetes or heart disease. It may be associated with chemical changes in the brain.
The brain is a complex organ. It controls all the workings of your body, including your emotions. It does this by using messages that travel from one nerve cell to another, and from one brain region to another. Brain messages travel with help from chemicals. These are called neurotransmitters. No one knows exactly what happens in the brain to cause depression. But we do know that neurotransmitters are involved.
Two neurotransmitters are the main ones involved in depression. These are norepinephrine and serotonin. Antidepressant medications and talk therapy (the main treatments for depression) both change the levels of these neurotransmitters, thereby relieving depression symptoms in many cases.