As a psychologist, I receive many phonecalls about parents who are worried that their child, teen is depressed. And part of the problem in assessing it is that most teens are somewhat moody. But there are certain signs you can use and should look at. If your child´s behavior has changed markedly, if they are much more irritable because one of the signs of depression in teens is irritability. Have their sleeping patterns changed? Have their eating patterns changed? Are they with a new group of kids? Has their school work suffered? So there may be a number of these signs which then should you lead you actually to speak to your teen. The problem is many teens do not want to talk to their parents about it. So one of the things I suggest is if you are really concerned, speak to your child´s pediatrician or family doctor. Get even a referral to a child or adolescent therapist where you could consult with them about your child´s symptoms or what you are seeing, and they could at least help steer you towards a certain direction. They may suggest that the child should come in. They may suggest let´s monitor things. But I always say to parents don´t live with a great deal of anxiety. Get a consultation. Speak to someone who really knows teens and then you can take it from there.