can a biological child from a good home have RAD?

RAD was recognised pretty early on (1950s) in children who were in hospital for months and months when they were babies, but went home to their biological family (though it wasn't called that then). So it's possible.But there are a whole slew of other disorders like ODD, pathological demand avoidance, and you've mentioned ADHD, which are not dependent on a reaction to something (RAD by definition is a reaction to something that happened).I know a lot of people now aren't sure that all kids who appear to have RAD actually do, some may have one (or more) of these other disorders (and their birth parents may have had it too which is why they could not care for them). I have heard of kids who were fostered at birth and really never saw their birth parents being diagnosed with RAD which doesn't really fit the definition, so it seems more likely that some children who are diagnosed with RAD because they are in foster care, actually have something else, than the other way round IYSWIM.