From WebMD: U.S. adults continue to rate obesity as the biggest health problem for children, according to a 2009 poll conducted by C.S. Mott Children's Hospital.
The complete list of children's health concerns rated as a "big problem":
1. Childhood obesity
2. Drug abuse
3. Smoking/tobacco use
5. Internet safety
6. Child abuse and neglect
7. Alcohol abuse
9. Not enough opportunities for physical activity
10. Teen pregnancy
DNA of children who experienced violence and bullying shows wear and tear that is associated with rapid aging http://goo.gl/FzY2i
Image source: Wikipedia, public domain.