dr. dana rabinowitz is a psychologist who treats kids with depression. hello, doctor. >> hi. >> so that we're all on the same page, what does "depression" mean? >> "depression" is one of those words that people use in everyday conversation to mean they feel really sad, but real depression is when you have a loss of interest in the things that you want, and you're sad for two weeks or longer. >> how can we tell the difference between just feeling blue and real depression? >> when you're really depressed, the level of depression is really intense. you feel so sad you can't find any interest in the activities you really enjoy. you might not be interested in school or your friends or your family anymore, and there are all these physical symptoms that go along with it, also. people can lose weight or gain weight. they can have trouble sleeping. they have trouble paying attention. they feel tired and fatigued and just generally feel lousy. >> how about your grades? does depression sometimes affect them? >> well, when you're depressed, you can't concentrate, an