Drug orphans younger than 5 are often found without clean diapers, are not toilet trained, and enough food or drink to live on. School-aged kids show no interest in school and are often absent, primarily due to the emotionally absent parent's indifference to his or her child's education, and sometimes due to the oldest kid's having to care for her younger siblings (mostly affecting girls).
Preteen or teen drug orphans show rebellious behavior, sometimes acting out in the exact same way their addicted parents do while at the same time raging at them for neglecting them. The parents are to blame for setting such a bad example. Other teen drug orphans will rebel by doing the exact opposite of what their parents have done: they live squeaky-clean; honor students, drug-free, alcohol-free, etc. These kids do not want to repeat their parents' mistakes, so they go to the opposite extreme. They're the ones with the character to rise above their poor or nonexistent upbringing to be somebody.