The causes of depression are not entirely understood. Things that may trigger depression include:

• Major events that create stress, such as childbirth or a death in the family.
• Illnesses, such as arthritis, heart disease, or cancer.
• Certain medicines, such as steroids or narcotics for pain relief.
• Drinking alcohol or using illegal drugs.

These and other factors can cause certain brain chemicals to get out of balance. As soon as the imbalance is corrected, symptoms of depression generally go away.

Clinical depression is a treatable illness marked by changes in mood, thought and behavior. That’s why it’s called a mood disorder. Everyone, at various times in life, feels sad or blue. It’s normal to feel sad on occasion. But what’s the difference between “normal” feelings of sadness and the feelings caused by clinical depression?

• How intense the mood is. Depression is more intense than a simple bad mood.
• How long the mood lasts: A bad mood is usually gone in a few days, but depression lasts for two weeks or longer.
• How much it interferes with your life. A bad mood does not keep you from going to work or school or spending time with friends. Depression can keep you from doing these things and may even make it difficult to get out of bed.