Depression is a common mental disorder characterized by sadness and lack of energy. It is a leading cause of disability worldwide.  In severe cases, it leads to 850,000 suicides around the world each year.

"[It] can affect their school, their relationships with friends, increased risk for suicide and increased problems with drugs and alcohol," explained Judy Garber, a doctor of psychology at Vanderbilt University. 

She presented the results of a study on teenagers and depression at a conference in New York. She studied teens because adults who suffer from depression say it often begins in adolescence.

"I'd like to eliminate the stigma that's associated with it because it is common, and it is treatable, and we think, preventable," she added.

Garber led a study on more than 300 teens who already had one episode of depression. Half the teens were in a control group.  The other half had regular group therapy that examined depression and taught coping skills, ways of solving the problems that caused their depression.

"We focused on looking at how they were thinking about things, particularly how they deal with stress, particularly when a stressor occurs," she explained.  "Do they they blame themselves, do they think that things are going to be terrible forever? Do they think that it's all their fault?  We get them to look realistically at what are the consequences of the events, consequences of their own actions, and then, what they can do about it."

When the study ended, those in the prevention program had an 11 percent lower incidence of depression compared to the control group. Garber points out that preventing depression has broad social implications.
Depressed teens sometimes act out and commit crimes. Preventing depression saves precious community resources.

Another thing the researchers learned: if a parent is depressed, teenagers were much more likely to feel depressed.  A parent's depression was such a strong factor that she says it prevented the program from helping these teens.

The researchers says their findings have the potential to improve the lives of many teenagers and reduce lost productivity when they enter the workforce.

The report is in The Journal of the American Medical Association.