No one is remotely interested in listening to me, but Oppositional Defiant Disorder is not something you can fix with a belt or a paddle. It is not caused by lax parenting or over permissive parenting, either. It is a disorder in the child's ability to process his/her emotional load.
It seems to me that ADHD and ODD, especially ODD can be incorrectly diagnosed when the situation arose that actually was the result of inappropriate parenting.
True, so can trauma symptoms be misdiagnosed as ADHD. Or, as you said, it could be a kid who has never been taught predictable rules and consequences (lazy parenting). It ain't easy to tease out which is which, I'm sure, but one would hope the professionals that gave the OP's nephew his diagnosis know what they are doing. A family practitioner might prescribe the meds but they would never make an ODD diagnosis themselves. It takes a child behavioral expert to do that, usually with a good deal of observation of the child in the home and school settings, time spent with the child, the parents, etc.
Here's a brain buster....
At what point do kids with trauma not get to inflict trauma on the rest of us.
In the real world, if you assault someone, the law does not care what your childhood was like.
In school, if you're traumatized, you can: kick, beat, hit, bite, throw things. run out of the school, choke, pull hair, sexually harass and all manner of things and NOTHING--and I mean NOTHING is done.
Everyone witnesses this. The other children do, of course, and that's not to mention the children who are not actually beat down. Teachers are regularly beat down. No one cares. Because, you know, the kids are traumatized, so if they want to beat the crap out of anyone else, who cares?
If we had any kind of decent media, they would be reporting this epidemic. But, they love them some Victims, and anyone traumatized is a Victim, so who cares if they actually, literally batter the heck out of everyone else?