Some of the commenters debated what Nadesan meant by a "looping effect." The phrase can refer to any self-reinforcing interactive process. In the context of autism, it could refer to disability stereotypes and the emotional effects of being told that one has a "mental disorder" that makes one behave in certain ways. It could be applied to more specific practices, such as behavioral therapies or the use of drugs to alter behavior.
Andrea just wrote a post in which she points out that there is also a looping effect that reinforces society's insistence on appearing normal. Because there is such strong cultural pressure to hide any differences that might be considered abnormal, most people rarely encounter anyone who does not appear to be within the realm of normality (wherever its boundaries, which often change, may be from one moment to another). This in turn reinforces a primitive fear of difference and the illusory perception that all people are very much alike.
Back when autistic traits were considered to be mostly normal (which was not all that long ago), it wasn't unusual for autistic patterns of speech and social interaction to be clearly recognizable in multiple generations of a family. There was also a looping effect at work there: parents who had autistic traits interacted with their children in autistic ways, such as quietly teaching by example and talking about ideas and values, rather than blathering on about celebrities and fashion and other such fluff. The children, in turn, were likely to develop a similar conversational style and a strong sense of their own identity, whether or not they would have been considered autistic by today's definitions. Because there was no reason to hide autistic patterns of speech and social interaction in those days, they were seen often enough to be viewed as part of the common landscape of normality.
I'm sure that we still have just as many multigenerational autistic families as we ever had, but now—in response to today's strong social pressure to hide or suppress autistic behaviors—many parents are denying their own autistic traits (whether consciously or subconsciously) and are making desperate efforts to transform their child into a more socially accepted type of person. As autistic traits have become stigmatized, those who display such traits are no longer welcome in the community; as a result, the only options that many parents can see for their children are to learn to pass for normal (that is, today's extremely narrow definitions of normal) or to spend their lives being hidden away from the world in institutions or group homes.
This has created a very profitable niche for behavioral programs such as ABA, in which, according to a therapist who was quoted in a Time Magazine article, 50 percent of the instruction focuses on teaching children "behavior to look good." ABA is not a medical treatment, as its advocates often claim; rather, it is a form of cultural indoctrination. After many years of intensive drilling in how to suppress their socially unacceptable real selves, some children, as discussed by Joseph and Not Mercury, will become so thoroughly assimilated into mainstream society that they ask to be "undiagnosed." Parents and psychologists often are happy to oblige.
Even more disturbing, as large numbers of autistics have had to suppress their natural behaviors, many people have become convinced that autistics never even existed. When the vast majority of autistic adults are "in the closet" for fear of being considered abnormal, it's not hard to convince people that there are no autistic adults; after all, that accords with what they see when they go about their daily business. Although scientific studies have clearly shown otherwise, the idea that autistic children suddenly appeared in the past few years perfectly suits the agendas of the epidemic-mongers who are raking in the profits from today's mass hysteria about autism. Once again, it's a "looping effect," and one that is quite likely to make the worldwide disappearance of a minority group—in what would be the largest genocide in history—go almost entirely unnoticed.