With regard to behavioral problems, adopted children are at risk than nonadopted children.

Adopted children are at somewhat greater risk than nonadopted children when it comes to behavioral problems.
This may happen because these children feel hurt due to their actual parents abandoning them so that they had to go to a new, foster family. Usually these children will use the classic 'You are not my real parents' excuse to do whatever they want and their parents will feel bad and thus not want to restrain them a lot.