Autism’s Hidden Hordes Wrongly Diagnosed?

Anti-vaccinationists frequently a quote the recent (the last 10 - 15 years) increases in autism as evidence that vaccines cause autism. Since virtually all good science contradicts this idea, it seems there must be another explanation for this apparent increase. One possible explanation is a change in diagnosis - children who are now diagnosed as autistic would have been diagnosed with a different condition 20 years ago. Anti-vaccinationists ask, “where are the hidden hordes?” – the adult autistics who were not diagnosed autistic as children. Because, if increases in autism are merely a change of diagnosis, then there must be numerous adult autistics who were not diagnosed as such as children.

Professor Dorothy Bishop of the University of Oxford, led a recent study to examine this question. The study was published this month in the Journal of Developmental Medicine & Child Neurology, and its conclusion was indeed to suggest that many children who would now be diagnosed as having autism, were in the 1980s and 1990s diagnosed with severe language disorders instead.

From the abstract we can see that Bishop looked at 38 subjects (aged 15 to 31), who had, as children, been diagnosed as having developmental language disorder, rather than autism. She then applied to them, modern tests for diagnosing autism at age 4 to 5 years – tests that involved interviewing both the subjects and their parents. The result was that one third of the subjects met the modern criteria for autism. The interviews with the parents were especially revealing: the subjects’ parents recalled what we would now regard as autistic symptoms appearing in their children when they were very young.  The conclusion is that much of the recent rise of autism could be due to a change in the diagnostic criteria.

The result is consistent with this study in Pediatrics from 2006 that showed the growing autism diagnoses from 1994 to 2003 were associated with corresponding declines in other diagnostic categories.

Of course the study needs replicating with a much larger number of subjects than 38, before any firm conclusions can be drawn. But the study’s tentative conclusion is consistent with the total lack of evidence that autism is caused by vaccines. To be sure, the anti-vaccine crowd would have been quick to publicize this study if the results had been negative, but now they will probably ignore the study, or criticize the independence of the study’s authors. That is their normal tactic when faced with studies they don’t like but have no evidence to refute. But what they won’t have are valid criticisms of the actual study, or studies of their own that show there was, in fact, no change in diagnostic criteria.

It would be nice if CNN and Larry King would now have Professor Bishop on to explain her studies to the public, and undo some of the misinformation they recently helped put out. But, again, we can be sure this won’t happen. They get higher ratings showing the idiotic views of “Professor” Jenny McCarthy.

References

Abstract: Autism and diagnostic substitution: evidence from a study of adults with a history of developmental language disorder

University of Oxford: Rise in autism related to changes in diagnosis

Comments

[King of Ferrets]

Of course, this won't put a dent in the Mercury Militia because they've made themselves impervious to logic. Kind of like being too stupid to die, but it actually works to a degree.

[DV82XL]

On the other hand there may well be an increase in autistic spectrum disorders, and this might be attributable to some environmental insult. However the anti-vaccination troopers have so deeply clouded the issue that few legitimate researchers will touch the subject.

I'm not suggesting that there is an external cause (or that there is in fact a real rise in autism) only that by politicizing bad science, these groups are keeping good science from being done.

[Joseph]

As I also pointed out in LB/RB, there are multiple studies of adults that are similar to Bishop's, going as far back as 1982. See my summary.

[tipsykw]

I just wanted to say that I do really like your blog--I wasn't just trying to be a pain the other day. Stuff like this is great, and should really be talked about more. It's a shame it's so hard to get sane, logical ideas out to the general public. I enjoyed the discussion, and I hope I wasn't rude! Thanks for blogging.

[Lenora]

I'm looking forward to when studies come out tracking the outcomes of all these kids diagnosed in the last 15 years. My kid diagnosed at three with mild autism would now at 10 more appropriately be labeled PDD-NOS; just like his father (a teacher) and grandfather (a German professor). I think many of the hidden horde are just living their lives passing as normal.

[pv]

I think many of the hidden horde are just living their lives passing as normal.

Since normal covers a multitude of sins, then why not?

[Heather]

Thanks for a great post. From here in Silicon Valley, the capitol of over-diagnosis, it's nice to see that there are people making sense.

[Citizen Deux]

Hooray! A sensible, easy to understand explanation for the "autism explosion". Far be it for the media to apply even the most basic of questions to this over-emotionalized topic.

Incidentally, I would love to see a post on abandoned medicines. I was in a 100 year old drug store today and they had a great display of old medicines. Many would be little more than "home remedies" (senna leaves as a laxative), save that they all bore the packaging of major pharmaceutical firms (Lilly, Merck, etc.).

Why did drug companies abandon these elixirs? And why do many of these older "medicines" resemble the snake oil being peddled by supplement manufacturers today?

[Patience]

Lenora, I whole-heartedly agree. I fit all of the diagnostic criteria for a mild case of Asperger's except the bits about being impaired by my differences. I've had to learn to act certain ways in public, but I'm not inhibited from a normal life. In fact, I'd go so far as to say that my being forced to learn to at least give the appearance of fitting in has benefitted me: I'm now a reasonably talented actress and am a, if not entirely comfortable, capable diplomat. I have to really pay attention to nonverbal cues and tone, and know when my breaking-point is so I can leave before I reach it.

Of my four friends (yes, I only have four people I'd call 'friends'), two also have the same pattern: meeting all the diagnostic criteria for Asperger's but also able to cope with symptoms well enough that they don't really impair daily life, and in turn a talent for acting and performing. All three of us are synaesthetes, too.

If there is a hidden horde, my personal suggestion would be to look in the theatres, playhouses, and drama departments. When you have to constantly watch, learn from, and mimic others for your social cues, you develop a lot of skill.