Teenagers often develop personal insecurities. It is due to the changes in their own body and their brain. How they think others see them start to play an essential part in their mind while building their own "self" vision. Consequences can be trouble to sleep, to the point of insomnia (I was sleeping 3 hours a night as a teenager even with sleeping pills at one point), aggression, withdrawal, and depression. If your child is facing those, speak with a professional who can help you understand them and teach you how to help them.