So, how do we help adolescents feel less depressed? If a lack of hope is seen as the cause of the depressed feelings, restoring that hope would be the answer. It needs to occur on two levels, societal and individual.
Mass alleviation of depressed feelings would need to be a concerted effort in which we help young people realize a baseline of hope. As frustrating as life can be, adolescents would feel that things are going to be okay, that their life always would be worthwhile. The only way they would feel so would be if their intrinsic worth wasn't based on proving it with success and achievement. They could experience a huge failure and still not see themselves as a failure. Unfortunately, that shift will require a wholesale change in our culture's way of viewing worth.
Individually, we can help each other them to the same place through all sorts of means. Our family and friendships probably are our biggest ones. They are best positioned to help us see our worth as an unequivocal, that is doesn't change based on our our mistakes or accomplishments. I would list quality work with a competent therapist as another means. A good therapist assists us in looking at ourselves and getting closer to a place of unconditional self-acceptance. These approaches are but two of many that are at an arm's reach.