After reading your comments on the possible link between immunizations and autism, I need to bring a few things to your attention. Autism is not a behavior disorder, as indicated in one portion of the article.
Autism is a neurobiological disorder that covers a broad spectrum of syndromes.
The regressive form of autism, where a child develops normally and then loses previously attained developmental skills, is not characterized by a child simply showing delays in language development. For children exhibiting the regressive form, adequate or even advanced speech skills fade and disappear. And yes, this typically occurs in the same time frame as MMR immunization. Examining children for symptoms only within a 28-day window of immunization seems too short a time frame to really determine if there is a connection. The congenital form of autism, where a child exhibits language delays from birth, would logically not seem to be a part of any discussion of immunization-induced autism.