When do I tell my child about his/her diagnosis?

Certainly any child with a diagnosis, who is aware enough to ask questions about it, should be told.  Most of the adults with PDD/Autism I know seem to agree that it is good to know about their diagnoses as early as possible. They talk about  the peace they've found within themselves when they have a word that describes themselves.  Children need to work through the same "process" we as parents do to deal with the fact that they  have an "invisible" disability.  There can be many of the same reactions such as sadness, denial, grief, anxiety, blaming the diagnosis for everything. These are stages that both you and your child have to go through to come to terms with the diagnosis.  Just remember your child is going through the same confused feelings you are going through.  One main difference:  you have a word to describe his/her condition.  

If a child is not told his/her diagnosis the door is wide open for that child and everyone else to suggest their own diagnostic labels with terms like lazy, stubborn, stupid, retarded, and far worse.  Teachers may suggest these (and more) labels.  Your child's peers may even suggest more damaging diagnoses:   Cooties, Retard, Weirdo, Mental, etc. This only destroys self esteem and confidence.  Any child who can't do things exactly like most child will feel he's "disabled", whether he is or not.  Your child already knows he's "different"  and recognizes that.  The only question is, what will he call that difference? "Autistic" or "PDD"  is a lot better than "lazy", "stubborn", "weird" or "mental".

Having a name for a reading difficulty such as dyslexia can be a beginning of knowing what to do next, and  ending the self-pity.  If I had no legs I would have no choice but to realize what my trouble is.  But with autism, especially the higher functioning forms like Asperger Syndrome or PDD-NOS, it is harder to know what the problems are.   A diagnosis should explain an obstacle to be overcome rather than impose a judgment.  Also, naming that obstacle automatically carries with it a list of methods of overcoming it.   Now, at this point,  information can be shared with others with the same diagnosis.  

Kids can be pretty resilient, as long as they're told (as much as possible, given age-appropriateness and capacity to comprehend abstraction) that a "condition" is how things are, and that anything that they want to do or be is achievable, just by using different methods from what they have been trying.  It's almost as if learning you need glasses: kids handle that one a whole lot better than most adults!  

There may be downsides to telling kids who they are, but I can't think of any right now.  I think it is worth the effort.  Also consider this:   by denying your child  the opportunity to know as much as he can about how he works, you're denying him the opportunity to do as much as he can with what God has given him.  Another item to consider:   that all kids, come up with their own explanations for everything.  If we, as adults, don't give them accurate information, then they will absorb inaccurate information.  Information that could possibly be very detrimental.  They don't stop thinking because adults don't talk to them.  

From a child's point of view, I think, it can be a great relief  (rather than grief, sadness, or anxiety)  if the communication of the diagnosis is conveyed with warmth ("Hey, you mean I'm not stupid?").  My wish for the future is that professionals would recommend that parents tell, and  advise these parents on how to tell, maybe even help them.