Can would-be patients or families dupe doctors like this all the time? How many more of the millions of kids diagnosed with ADHD and bipolar disorder carry their diagnoses as a result of parental reporting alone, with whatever biases might be present? Is there a way for child psychiatrists to filter out parental bias?Remember that when kids are quite young (like four years old), they don't have the cognitive skills to report on their own symptoms all that accurately. Yes, the kid should be interviewed, but don't expect much. So, that naturally causes mental health professionals to rely on parent reports. Should doctors try to obtain collateral information? Yep. Teachers, friends' parents, babysitters. It is interesting that parent, teacher, and child reports of children's behavior often differ quite a bit (1, 2, 3). Why?
Environment: Well, the environment impacts behavior. If the parents have a chaotic home environment where discipline is inconsistent, expectations are unclear, and negative emotions run high, then the kid has a better chance of showing a variety of behaviors and emotions that could come across (rightly or wrongly) as some sort of mental disorder. If these same symptoms are not expressed at school, then maybe the controlled environment, positive peer interactions, relationship with the teacher, teacher's strong classroom management skills or whataver are helping Junior keep a lid on the problem behaviors at school. So if the kid can keep it together at school but not at home, is this the kid's problem or the parent's problem?
But teachers are not always tuned in all that well to all students' behavior and certainly not to all of their kids' emotional state, as their job is not to play psychiatrist to kids, but to teach. So their ratings will not be completely accurate either. My personal belief is that getting opinions of teachers (note the plural), parents, the child, and whomever else spends significant time with the kid is much better than relying on the point of view of just one source.
Making Up Symptoms? There will always be bad apples who fabricate symptoms in their kids. I've seen little evidence that such behaviors are common. It is more common that parents don't set up a solid discipline system (discipline, by the way also involves positive reinforcement, not just punishment) and develop strong relationships with their kids. One can also not discount peer influences, especially as kids get a bit older. Bad peers can lead a reasonably good kid down a pretty bad path. I'm also pretty sure that a steady diet of McDonald's, Grand Theft Auto, and other brain-numbing delights is probably not good for development in general and that our lazy-ass American lifestyle could have something to do with some of these cases.