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Social Factors in Autism Diagnosis

There is no question that the incidence and prevalence of autism are on the rise. Starting in the early 1990s and continuing to today, there has been a steady rise in the number of children diagnosed with autism. Prior to 1990 the estimates of autism prevalence were about 3 per 10,000. The most recent estimates from the CDC and elsewhere now have the number at about 100 per 10,000, or 1%.

The burning question is – why are the rates increasing steadily? There are those, particularly in the anti-vaccine community, who conclude that the increase in prevalence is a real biological effect – an epidemic – and is evidence for an environmental cause (which they believe is vaccines, even though the scientific evidence does not support this position). However, the evidence strongly suggests that the rising prevalence of autism is largely an artifact of broadening the diagnosis and increased surveillance.

It should be noted that the data cannot rule out a small true increase in autism prevalence. Some hypothesize that increasing maternal and paternal age are contributing to the incidence of autism, but I will leave that question for another post.

A new study now adds significant support to the surveillance hypothesis – Ka‐Yuet Liu, Marissa King, and Peter S. Bearman from Columbia University, publishing in the American Journal of Sociology, report that the risk of being diagnosed with an autism spectrum disorder (ASD) correlates with social proximity to another family with a child with an ASD diagnosis. For those interested in this topic, the full paper is worth a read. While it gets technical at times, the authors do an excellent job of reviewing this topic in detail.

To summarize their key points – they begin by reviewing the history of the autism diagnosis. They point out that historically, in the 1950s and 60s, the diagnosis of autism was stigmatized by psychogenic theories of causation (the infamous “refrigerator mothers”). But then:

With hindsight, we can recognize that autism was increasingly destigmatized through the mobilization efforts of Bernard Rimland and the National Society for Autistic Children (NSAC), whose work refuted psychogenic theories of autism and set the stage for the research program that would identify autism as a neurological disorder (Dolnick 1998).

Therefore, prior to the 1970s parents actually mobilized their resources to avoid an autism diagnosis, and instead to seek a diagnosis of mental retardation (MR). This was not only to avoid stigma – the diagnosis of MR was attached to more public resources, while autism was left out in the cold. Then, this situation began to flip. Increasingly after 1990 ASD lost its stigma and became increasingly attached to access to public resources. Parents then began marshaling their resources to obtain an ASD diagnosis, rather than an MR diagnosis.

Liu et al discuss that this interpretation of the history of ASD makes a number of predictions, and they sought to test those predictions. They are not the first to do so, and others have demonstrated (which they review) that as ASD diagnoses increased there was diagnostic substitution – other related diagnoses, such as MR, decreased. Autism prevalence has increased uniformly in all age groups. If an environmental cause was at work, younger age groups should have disproportionately increased. When the same diagnostic criteria are applied autism incidence is largely stable over time. Increasing caseloads of ASD correlate with times when the diagnostic criteria are expanded.

The study authors now go further – looking at the pattern of ASD diagnoses sociologically. They hypothesized that if the increasing rate of ASD is due to sociological, rather than biological, factors then proximity should play a role. That is exactly what they found – a child who lives 250 meters from another child who has been diagnosed with autism is 42% more likely to be diagnosed, and if they live between 250 and 500 meters of another child, they have a 22% increased chance of being diagnosed. Basically, being close to a family with an ASD child provides access to information that allows other parents to more efficiently mobilize their resources to seek an ASD diagnosis.

This matters because obtaining an ASD diagnosis is not always easy or automatic. Many ASD children, on first presentation to a pediatrician, are not diagnosed. Some doctors are more likely to make the diagnosis than others. And school systems may delay diagnosis as well. Parents who therefore pursue a diagnosis more aggressively are more likely to get it.

Of course, an infectious agent would also spread through proximity, so they tested this possibility by looking at specific features that should differ. For example, the sociological spread hypothesis predicts that the proximity effect should be greatest at the milder end of the spectrum. More clear cut cases are likely to be diagnosed regardless of parental resources or effort, while milder cases will be highly dependent on these factors. They found that the proximity effect existed only among the milder end of the spectrum, and was absent for more severe children. They also found that the effect obeyed school districts – so proximity across a school district demarcation did not confer increased chance of having an ASD diagnosis. Further, they found that children with an ASD diagnosis had similar referral sources to other ASD children with proximity.

All of this points to the fact that parents obtain information from other parents in their neighborhood about which doctors to see, what questions to ask, and how to interface with the school system most effectively to obtain an ASD diagnosis and the increased services that come with it.

Conclusion

This study adds powerful evidence to the conclusion that the increasing incidence of autism is largely due to sociological factors rather than a true increase in the incidence of autism. This does not rule out a true increase also hiding in the data, but rather demonstrates that sociological factors are a significant contributor. This study must also be put into the context of the many other studies supporting the conclusion that the dramatic increase in ASD is due largely to increased surveillance and expanded diagnosis.

I was also not previously aware of the extent of the effect that social stigma has played. Previously parents avoided an autism diagnosis and sought an MR diagnosis, while today the situation is reversed, and the evidence shows the diagnostic substitution we would expect to be the result.

Another prediction of the sociological hypothesis is that eventually autism incidence should level off – once diagnoses are saturated. We are probably getting close to that point now.

All of this also means that scientists are justified in focusing their research efforts on characterizing the genetic risks and causes of ASD. Further, calls for a shift in emphasis to environmental causes based upon the premise that there is an autism epidemic are not valid in light of this research. This does not mean that environmental contributors should not be explored – it is often practical to cover all the bases in medical research – but a significant shift in resources is likely not justified.

Posted in: Neuroscience/Mental Health, Vaccines

Leave a Comment (57) ↓

57 thoughts on “Social Factors in Autism Diagnosis

  1. Esattezza says:

    Great post, Steve, thanks. I know what article I’ll be reading while my PCR runs now… :D

  2. marc says:

    Great post, Steve. Now the real question–was the autism “tsunami” therefore a result of this effect writ large by the likes of JB Handley and Jenny McCarthy going on every talkshow they could to promote autism awareness? It seems very likely that instead of vaccines, the anti-vaxers themselves may be more responsible for the rising diagnosis curve, which would be deliciously ironic.

  3. orange lantern says:

    Good stuff. I really feel that this angle of the autism “epidemic” is vastly underappreciated. Every media bit about vaccines and autism, even if it is not antivax, charges right into the autism epidemic as if it were a given.

  4. mikerattlesnake says:

    I think there’s only one logical conclusion: vaccines are curing mental retardation.

  5. Erika says:

    These are powerful arguments, but I can still see non-epidemiologists and/or those in the autism/mercury/environment community looking at the proximity data and arguing that these “autism clusters” indicate environmental causes (such as mercury, electrical lines, etc.) rather than sociological. (Just to be clear, I’m not in that camp.)

  6. Galadriel says:

    Did “Rain Man” make a difference in diagnosis rates, I wonder?

  7. Good Article Dr. N. I have been wondering about this lately. My son has a speech impairment due to cleft lip and palate, he recieves speech pathology services through the school system and the hosptial cleft clinic.

    I think he’s been informally evaluated for Autism about five times (he’s five) due to his speech issues. One center where he received speech therapy had non SP staff that routinely referred to his autism (which he doesn’t have). I think, this was due to the fact that they have such a high rate of Autistic students.

    While I have no problem with someone screening my son for a condition, when he has one indication, I sometimes felt concerned at the possibility that some children with more difficult to diagnoses conditions might get tracked into a Autism diagnosis and be given the wrong services or therapies. Perhaps children with conditions like Aphraxia or other language, speech or hearing disorders.

    But then most of my personal experience is the speech/language area, so maybe my that is not representative.

  8. provaxmom says:

    Kim Peek (Rain Man) just died recently. He was actually missing a corpus callosum, which is fascinating to me.

    Regarding:
    “That is exactly what they found – a child who lives 250 meters from another child who has been diagnosed with autism is 42% more likely to be diagnosed, and if they live between 250 and 500 meters of another child, they have a 22% increased chance of being diagnosed. ”

    Does this mean that ‘teh autism’ is contagious? :)

    If Asperger’s is dropped from DSM, what effect do you think that would have on this?

  9. AlexisT says:

    How about the influence of the availability of therapy and educational support? Anecdotally, I’ve heard of a preference for autism spectrum disorders because it’s easier for the kids/parents to get help.

  10. Martin A. Lessem, J.D. says:

    Another interesting Kim Peek note, it is thought that he did not have an ASD, but rather FG Syndrome.

    Opitz JM, Smith JF, Santoro L. The FG syndromes (Online Mendelian Inheritance in Man 305450): perspective in 2008. Adv Pediatr. 2008;55:123–70. doi:10.1016/j.yapd.2008.07.014. PMID 19048730.

  11. Todd W. says:

    @Erika

    The researchers anticipated that contention:

    Environmental toxicants should be largely insensitive to social boundaries like school districts, but social influence should not be. We find that while parents’ proximity to a child within their school district increases the chances that their child will be diagnosed with autism, equally close proximity across districts has no effect.

  12. passionlessDrone says:

    Hello friends –

    Is there anyone out there that has a child on the spectrum that can relate whether they met another autism parent before their child was diagnosed?

    My son has autism, but I can tell you without a doubt that I knew zero children with autism before my son was diagnosed, 1 kilometer from my home, or 100. I live in a small city of around 250K people. The local university has a CARD center, who was blanketing pediatricians with forms to return looking for toddlers with red flags, we filled one out, which eventually led to his diagnosis. I now know about twenty (?) families with kids with autism, I’ve been to seven or eight of their houses, but all are much more widely distributed than indicated here; some may share things like playgrounds, I suppose. (?) I don’t know what my son would have been diagnosed with had we not had a CARD center, but he would have gotten something.

    I’m also wondering if there is anyone out there that really felt like an autism diagnosis was giving their child any meaningful service level benifits in the early 2000′s? Again, my experience was that services provided by either the country or state are tragically underpowered; there I was reading that the ‘experts’ recommended a child get 40 hours of ABA a week, but after having no less than 4 IEP meetings over six months, Luke was finally, finally given an ‘educational’ diagnosis of autism, and had a speech therapist assigned to spend thrity minutes a week with him. Three more years into the school system he now gets an hour and a half of speech / OT within the public school system.

    The recent legal moves in my state (Florida), have mandated that autism be covered for traditional therapies (i.e,. speech, ABA), but this was a very recent event, and in fact, despite being law for four months, and pending for eighteen months, we’ve yet to have BCBS accept a claim.

    Maybe others have had different experiences (?), but the idea that there are parents out there recommending other parents seek out an autism diagnosis so that they access all of these great services is highly discordant with my experience, and the experiences of people I know with children with autism.

    As far as the ubiquity of environmental exposures across areas, I ran into this paper a few weeks ago that described racial, cultural, and socioeconomic determinants in the body burdens of a variety of endocrine disruptors and pesticides.

    http://www.ncbi.nlm.nih.gov/pubmed/20129604

    This was a very thoughtful analysis. Thank you for posting it.

    - pD

  13. TsuDhoNimh says:

    So mild autism is “viral” … in the information sense.

  14. bkates says:

    Just a small clarification: school systems don’t diagnose; they (we) apply labels that seek to describe a child. It’s quite separate from the medical diagnosis process. A medical diagnosis of autism (or PDD) is a requirement in most places to be labelled with ASD in schools but that same diagnosis does not ensure the school label. This is largely because the disability must have some educational effect. For instance, one could be a wheelchair user without any negative educational impact. In this case there would be no access to services.

    Great post by the way.

  15. Kristen says:

    Thank you Dr. Novella for this great article. I find this to be true in my case (anecdotally of course) because after Gabriel was diagnosed my nephew and husband were also found to be on the spectrum.

    This matters because obtaining an ASD diagnosis is not always easy or automatic. Many ASD children, on first presentation to a pediatrician, are not diagnosed. Some doctors are more likely to make the diagnosis than others. And school systems may delay diagnosis as well. Parents who therefore pursue a diagnosis more aggressively are more likely to get it.

    This is very true. It took my Gabriel getting kicked out of two preschools and quitting my job (that I had just gotten) to finally get the doctor to say something might be up. Then I had to fight to get him in to see one of only two Developmental Pediatricians in our area. Then it only took him a half hour of observation to say “your son has autism”.

    One of the parents I met at the second preschool was the first to mention autism and give me the name of the Developmental Pediatrician her daughter saw.

  16. Sid Offit says:

    Therefore, prior to the 1970s parents actually mobilized their resources to avoid an autism diagnosis, and instead to seek a diagnosis of mental retardation (MR).

    This was not only to avoid stigma –

    ——————————————

    Less stigma attached to mental retardation? Are you serious? Back in the day, there was nothing worse than being diagnosed as retarded. And how could autism have a stigma when no one knew what it was? Your post illustrates the lengths deniers such as yourself will go to convince themselves that there’s no autism epidemic.

    Yeah, there was no stigma being called mentally retarded. This in the era of Geraldo Rivera’s expose reveling the horrors of the Willobrook mental institution.

  17. Erika says:

    Todd W., thanks. I missed that. Thanks!

  18. orange lantern says:

    Sure, that has a stigma attached to it. But autism was associated with an even worse stigma, that of “refrigerator mothers”.

    Because of this stigma, and the fact that autism was poorly understood, and there were not special resources in place for autism, parents and physicians were not driven to seek an autism diagnosis instead of MR.

  19. Sid – read the paper, they go into detail.

    The cause for the increased stigma attached to autism was the fact that it was believed to be caused by bad parenting – so what parent wants that label? Further, this led to the conclusion that autism was not deserving of resources.

    An MR diagnosis was not desirable, of course, but MR was thought to be biological – not the parents’ fault. And therefore came with more funding for services. In fact MR advocates – according to the article authors – lobbied against resources for autism because they felt it was not a “real” disorder like MR.

    Bottom line – parents of atypical children were motivated to avoid the diagnosis of autism in the past, now they are motivated to seek it.

  20. bkates – you are correct, schools do not diagnose, they label.

    But – the “rise in autism” is based largely on numbers from kids registered for services, not formally medically diagnosed. The recent surveys that found 1% of kids have ASD asked only if they have ever been given an ASD diagnosis – including by the school – not restricted to formal medical diagnosis.

    Drone – your experience is anecdotal, and services vary greatly by state, so that may have something to do with it.

  21. lonnie123 says:

    Dr Novella,

    I thought I had read recently that they were looking into the increase in maternal age as a possible piece of the puzzle, which sounds highly plausible to me to account for at least a portion of the increasing numbers. Have you heard any info about this line of inquiry?

  22. Martin A. Lessem, J.D. says:

    Sid Offit states: “And how could autism have a stigma when no one knew what it was?” regarding the era prior to the 1970′s mentioned in Dr. Novella’s article.

    This is why I love what I do for a living ;) (Regulatory Attorney for a Pharmaceutical Company) (aka – I get to research fun things like this on the Interwebs)

    Does the word Autism need to be known for a disease to be diagnosed as such?

    If so, the earliest diagnosis of Autism occured in 1943 by Dr. Leo Kanner in 1943 when he assigned the label of “early infantile autism” to 11 children(1). Dr. Hans Asperger had, in 1938, used Dr. Eugen Bleuler’s term “autistic psychosis”(2) in a lecture at the Vienna University Hospital(3).

    If, on the other hand, the word Autism does not need to be know for a disease to fall within the bounds of it, the we can go back at least as far as 1747 to the case of Hugh Blair of Borgue(4). Ironically, this is a court case where Hugh’s brother attempted via petition to have Hug’s marriage annulled to be able to acquire the inheritance after their family for himself.

    So was, as Mr. Offit posits, autism not known before the 1970′s? Based on the above, I would have to say, no.

    Hope this helps ;)

    (1) Kanner L. Autistic disturbances of affective contact. Nerv Child. 1943;2:217–50. Reprinted in Acta Paedopsychiatr. 1968;35(4):100–36. PMID 4880460.
    (2) Kuhn R; tr. Cahn CH. Eugen Bleuler’s concepts of psychopathology. Hist Psychiatry. 2004;15(3):361–6. doi:10.1177/0957154X04044603. PMID 15386868. The quote is a translation of Bleuler’s 1910 original.
    (3) Asperger H. [The psychically abnormal child]. Wien Klin Wochenschr. 1938;51:1314–7. German.
    (4) Houston R, Frith U. Autism in History: The Case of Hugh Blair of Borgue. Blackwell; 2000. ISBN 0-631-22089-5.

  23. SkepticalLawyer says:

    @passionlessDrone:

    I met two children with autism before my child was diagnosed. One was before we had any suspicion that something was unusual with my child, and one after I thought we needed to get him evaluated. I also saw a Nightwatch episode on autism, which made me start thinking that that might be what my son had.

    My state is excellent for services. In the early 2000s, we were able to get over 20 hours of ABA per week, speech therapy, occupational therapy, and other developmental therapy. I know parents who moved from Florida because of the lack of services there.

    I know that I have also recommended to other parents that they consider getting a developmental and neurological evaluation of their children when something seems amiss.

    I don’t know what the case is now, but back in 2000 to 2001 our pediatrician was very reluctant to say that there might be a need for an evaluation of my son, even when he wasn’t talking–not a single word–at 18 months old. I think pediatricians are much more aware of developmental delays now, and are less hesitant to recommend further evaluations.

  24. overshoot says:

    Lovely paper. I know a sociologist who can use this as a great example of good scientific methodology in sociology. Alas, the subject comes up frequently and this is actually a great topical citation for her introductory students.

    Thank you for pointing this one out.

  25. Sid Offit says:

    I re-read the paper’s references to stigmatization and still see nothing more than speculation.
    —————————————-
    For several decades after its initial identification in 1943, autism was thought to be the by‐product of the response of children to the double bind of cold and ineffective parenting, a view initially promoted by Kanner (1949) and later by Bettelheim (1967) with the imagery of the “refrigerator mother.” Throughout the 1950s and 1960s, whole generations of American parents of children with autism suffered stigmatization (Bettelheim 1967)
    ——————————————-

    Where were the autistics before the ascendance of the refrigerator mother theory in the 50s

    Where is the evidence that doctors were unwilling to hurt the feeling of parents by giving them an accurate diagnosis?

    http://www.jstor.org/pss/1449786
    Why did autism rates not explode after a biological basis for autism was established in the 70s

    ———————————-

    MR was losing much of its stigma as a powerful advocacy movement took hold and garnered a wealth of resources for people with MR. Between 1948 and 1966, the number of children with MR in public school classrooms increased by a factor of five because of the political and administrative success of MR advocates in securing special education classes

    The sad fact is that, in the 70s, regardless of the resources and educational opportunities available MR was highly stigmatized

    ——————————

    The theory of ever-present autism may be correct but it must be proven with empirical evidence rather than unfounded speculation

  26. This would have been a cool way to analyze incidence back when everyone was getting diagnosed with multiple personality disorder and or ritual satanic abuse. My own idea was to consider the MPD-believing therapists (Bennett Braun, Judith Peterson, etc.) as some exposure source infecting their clients with MPD-pattern symptoms through the power of suggestion and other strategies that parallel brainwashing techniques.

  27. Todd W. says:

    @pD

    If you read the paper, you’d note that they discussed limitations to their findings, including that their results were rather specific to California. Further, studies such as this are generalizations. There will always be outliers. Individual experiences may vary, to steal from a variety of TV commercials.

  28. Sid Offit says:

    @Martin

    So was, as Mr. Offit posits, autism not known before the 1970’s? Based on the above, I would have to say, no.
    ————————-
    When I stated “How could autism have a stigma when no one knew what it was,” I assumed Dr. Novela’s “stigma” applied to the community’s perception of an autistic child not the stigma of being labeled a “refrigerator mother”

    Anyway, I never said autism was unknown prior to the 70s. I wondered how it could be stigmatizing if no one in the community was aware of what it was.

    This, from the blog of a parent with autism, should illustrate my point:

    I remember the first time I heard the word Autistic.

    I was completely oblivious about the meaning and significance of that word.

    My brother was the first one to suggest to me that my daughter might have Autism.

    This was about 11 years ago.

    A decade has passed and many children are currently being diagnosed with this disability.

    However, there are still a lot of people that are just as clueless today as I was back then.

    It amazes me that despite the statistics being 1 in 150 children having Autism many people still don’t know what it is.

    Sometimes when I’m out with my daughter people will ask me why is she behaving that way?

    I will tell them because she is Autistic and you should see the look on their face.

    Many will say- oh ok she is artistic but why is she screaming?

    I will go on to repeat myself…NO Autistic NOT Artistic.

  29. SkepticalLawyer says:

    @Sid Offit:

    The stigma-related discussion that you have glommed onto was not the “evidence” in this study. If you read Dr. Novella’s post again (I haven’t had time yet to read the study itself), he says that the stigmatization helped the researches form the hypothesis that real autism rates have been constant over time. They made some predictions from this, namely that the rate of MR diagnoses should have decreased at about the same time that the rate of autism diagnoses increased and that the sociological effects would be there. Their research then confirmed the predictions (or so they say). That’s the evidence that you seek.

    Just as an aside, I used to work in child protection. I have seen many doctors and therapists do their best to defend parents from any idea that they have been abusive or neglectful. I can completely understand how a doctor who likes and trusts a parent would seriously hesitate to diagnose a child with autism if the prevailing scientific view at the time was that autism was caused by bad parenting.

  30. passionlessDrone says:

    @SkepticalLawyer –

    Wow! I’m very jealous. What a difference a state line makes. Thanks.

    @Todd W –

    If you read the paper, you’d note that they discussed limitations to their findings, including that their results were rather specific to California

    OK, I did try, but that was a pretty big one to get through during lunch. [Maybe I'll try again tonight.]

    Anyways, I’m interested in your thoughts as far as being specific to California; doesn’t that portend to problems if, for example, we observe the same increased rates of autism in Boca Raton, where your mailbox is just as likely to be 500 meters from your house as another household? In other words, if we can remove the physical proximity effect simply by moving to an area that still has observed rising per capita autism rates, what does this tell us about it’s usefulness as a metric? Is this simply another way of measuring urbanicity?

    Thanks.

    - pD

  31. passionlessDrone,

    I would think that the fact that your son received an autism diagnosis subsequent to an outreach program actively seeking out possible autistic children is support for the idea that the increase in austim diagnoses is a result of active seeking.

    For instance, the original paper mentioned that children with diagnoses of autism tended to share the same referral sources — exactly your experience.

  32. Wolfy says:

    “However, the evidence strongly suggests that the rising prevalence of autism is largely an artifact of broadening the diagnosis and increased surveillance.”

    Thank you for raising this very important point.

    In the same manner, if we continue to lower the fasting and random blood sugar cutoffs, we’ll diagnose more people with diabetes. . .but I’m sure some yutz in Hollywood will do his/her best to convince everyone out there that diabetes is on the rise because we’re not eating the right vitamins :)

  33. passionlessDrone says:

    Hi Allison Cummings –

    I would think that the fact that your son received an autism diagnosis subsequent to an outreach program actively seeking out possible autistic children is support for the idea that the increase in austim diagnoses is a result of active seeking.

    Indeed, it did occur to me that the ‘greater awareness’ phenomena could be attributed to my son’s diagnosis. It is also, however, possible that such active seeking is the result of an actual increase in the number of children with autism.

    This paper is attempting to assign some very specific mechanisms of awareness, spatial proximity to another child with a diagnosis and parental advice, and claims to find very significant drop offs in risk of diagnosis the further you move away from another child with a diagnosis.

    I don’t doubt that social factors are contributing to our observations of higher rates of autism, but I do have problems with the idea that such drastic changes are only applicable to certain areas, but not to others. Shouldn’t we see a steep drop off in a town like mine, where no one can walk to their pediatrician, or grocery, or playground?

    Of course, it is possible that the CARD center outreach in my area just happens to provide equivalent awareness as parents that interact with each other in densely populated Los Angeles. (?) It might be interesting, for example, to attempt a similar outreach in pediatrician offices in and around this study area, and subsequently see if the space proximity effect begins to deteriorate. (theoretically)

    Eventually, I believe that a bioinformatic approach will answer this question about our observations of autism rates. As long as we are dependent on measuring factors as maleable as greater awareness and diagnostic criteria as fluid as the spectrum, we really just guessing.

    Thanks.

    - pD

  34. provaxmom says:

    My son’s Dx is really not relevant here, he was Dx at 10m. He wasn’t hitting milestones. Yes, I had/have friends with ASD, kids with ASD, but that’s not the Dx I was seeking. I wanted to know why my kid wasn’t rolling over at 6m or sitting up at 8m.

    He just happened to have the ‘most frequently identified chromosomal disorder with individuals with autism.’ But that’s not what I was seeking. If I’m being honest, I had hopes that his developmental delays were just that, delays, and that he would catch up. :(

    I live in metropolitan Philly, and yes, we have decent services. But everywhere you read, ABA is the way to go, yet no one can afford it and few insurances cover it.

  35. William Stewart says:

    Dear Dr. Novella and discussants,
    Regarding the evidence (or lack of it) for an epidemic of autism, I recommend the following article:

    M. A. Gernsbacher, M. Dawson, and H.H. Goldsmith, 2005. Three Reasons Not to Believe in an Autism Epidemic. Current Directions in Psychological Science, vol. 14 (2), pp.55-58.

    Although not relevant to the cogency of their arguments, it is of interest to note that the first author is a past president of the Association for Psychological Science and is the mother of an autistic child. The second author is an autistic person. For very interesting articles on autism, I also recommend the first author’s website.
    I access this website and Neurologica almost every day.
    Cordially,
    William Stewart

  36. mikerattlesnake says:

    @Drone

    you do have things like television and the internet in your town, right? While proximity may hasten the process, there are certainly plenty of ways for awareness of the symptoms of autism to disseminate through more rural areas.

  37. mikerattlesnakeon 15 Apr 2010 at 9:15 am

    “@Drone

    you do have things like television and the internet in your town, right? While proximity may hasten the process, there are certainly plenty of ways for awareness of the symptoms of autism to disseminate through more rural areas.”

    This is true, but not really valid in relationship to the Social Factors report, since they were looking at proximal groups. TV and internet are across proximal groups.

  38. somewhat related, but not the same: i have been involved in psych care in some way or another since late 1980s. back in the day, no one ever talked about “cutting,” and it was really infrequent. sad to say that this behavior got a lot of attention – “we” used to see it as confirming “borderline personality disorder,” and we would assume this until proven otherwise (of course, we also used to assume “antisocial” if there were 2+ tattoos until proven otherwise; now 2+ tattooos just means under 28yo and not home-schooled).

    if you talk to a group of high school girls, they are quite familiar with cutting among their cohort. a couple will be able to show you their faint scars. it used to freak me out, indicating at the very least a very serious level of psychopathology, but now i mix the social-contagion/popularity idea into my info-gathering and conclusion-making. a few will also show you their tattoos.

  39. Todd W. says:

    @pD

    Anyways, I’m interested in your thoughts as far as being specific to California; doesn’t that portend to problems if, for example, we observe the same increased rates of autism in Boca Raton, where your mailbox is just as likely to be 500 meters from your house as another household? In other words, if we can remove the physical proximity effect simply by moving to an area that still has observed rising per capita autism rates, what does this tell us about it’s usefulness as a metric? Is this simply another way of measuring urbanicity?

    Well, I’d say that the results are interesting and sound rather plausible. Other studies in different locales using the same methodology would, I think, be a good move to determine how valid the conclusions are.

    Getting to the proximity aspect you raise, how would you propose removing the effect? If an area has rising per capita autism rates, and you move there, the effect will still be present, if the conclusions the research team reached are valid. So, by moving to such a locale, the likelihood of receiving a diagnosis of autism would increase.

    Further, if proximity is a risk factor, then we would expect to see higher rates in more heavily populated areas (urban and suburban) than in rural locales. In other words, where there are greater awareness and social resources (Drs. and others knowledgeable of autism diagnosis, social services, etc.), there is greater occurrence of autism diagnosis and seeking of support services.

    So what would this suggest? That there may be just as many autistic individuals in rural locations as in more populated areas, but they are not being diagnosed. It also suggests that it is more likely for an individual to be misdiagnosed in a rural location, thus falsely inflating the numbers.

  40. joseph449008 says:

    There is no question that the incidence and prevalence of autism are on the rise.

    I’d like to nitpick the accuracy of this statement, Dr. Novella. Sure, the administrative prevalence and incidence are on the rise. The prevalence ascertained by means of passive systems might be on the rise. But if you go and fully screen a population of children today, and you do the same thing with the same methods and tools a few years from now, there’s no reason the prevalence should rise, and there’s no evidence that it has risen when the same methods and criteria are used.

  41. mikerattlesnake says:

    @# micheleinmichigan

    While that may be true, she seems to be assuming that without proximity there is no way that a rising awareness of autism could spread to a rural community. I was pointing out that while this study may not be replicable in her region, it doesn’t mean that the underlying hypothesis is wrong. Media attention and the internet could set a pretty high baseline of awareness that is only augmented by proximity. Hence, an overall trend of increasing diagnosis with areas of concentrated diagnosis.

  42. mikerattlesnake – Oh, I see what you are saying now. Thanks for the clarification.

  43. passionlessDrone says:

    @Milkerrattlesnake –

    you do have things like television and the internet in your town, right? While proximity may hasten the process, there are certainly plenty of ways for awareness of the symptoms of autism to disseminate through more rural areas.

    They have TV and the Internet in Los Angeles too, but they still found a forty percent increase due to a 500 meter spatial proximity. If TV and the Internet are so good at raising awareness in my area, how come it hasn’t had the effect of reducing the spatial proximity effect in Los Angeles? If the TV and Internet aren’t good at raising awareness, and the spatial effect really is that strong, shouldn’t the rates of diagnosis be much lower in my area, where people are spatially distributed in much higher areas?

    While that may be true, she seems to be assuming that without proximity there is no way that a rising awareness of autism could spread to a rural community. I was pointing out that while this study may not be replicable in her region, it doesn’t mean that the underlying hypothesis is wrong.

    Your understanding of my assumptions are incorrect. I am trying to understand the problems with assigning risks to areas that the authors acknowlege apply only to very special demographic definitions against a backdrop of widespread increases in autism rates across all demographic areas. The authors make the claim, in fact, that rates in California are lower that average.

    In California—where autism prevalence is lower than the national average—the number of autism cases handled by the California Department of Developmental Services increased 634% between 1987 and 2003 (California Department of Developmental Services 2003).

    The authors are claiming that spatial proximity is having a big impact on rising rates:

    An underlying social influence mechanism involving information diffusion drives this result, contributing to 16% of the increase in prevalence over 2000–2005.

    What does this mean to my community, where spatial differences can’t be having such wide ranging effects, but none the less, we are also experiencing widespread rises in autism diagnosis? What something else responsible for this contribution in my area? If it is something as simple as TV and Internet, shouldn’t it have had an effect in someplace like Los Angeles as well, in essence, negating the effect of spatial proximity?

    Sixteen percent of the observed rise is a very powerful effect; I’m only saying that we should have good reasons that we can apply this magnifier only in very narrow bands of the map, and ignore it everywhere else. The fact that there are other means of social influence isn’t robust enough, those should be acting within city centers also.

    @Todd –

    If an area has rising per capita autism rates, and you move there, the effect will still be present, if the conclusions the research team reached are valid. So, by moving to such a locale, the likelihood of receiving a diagnosis of autism would increase.

    But look how steeply the effect drops off after only 250 meters in this study, again at 500 meters, and steadily declines.

    Compared with children who are 501 meters–1 kilometer away from their nearest neighbor with autism, those in close proximity (1–250 meters) to a child with autism have a 42% higher chance of being diagnosed with autism in the subsequent year. Proximity of 201–500 meters increases the chance by 22%

    If someone with autism moved into my neightborhood, four houses down they would be more than 500 meters from my house. Taking the birds eye view, there may be a total of five other children living within 250 meters of my home; does anyone out there really believe that the day my son got diagnosed, those five children had their risk of a diagnosis within the next year increase by 42%?

    Again, I’m not arguing against a social component to rising rates, but this one seems to run into problems when we want to apply it anywhere outside of city centers, and autism rates are rising in places other than that.

    - pD

  44. mikerattlesnake says:

    That the rates are rising in both areas is not in contention, but when you state that they are rising at the same rate I wonder what you are basing that on (maybe I’m forgetting a statistic you have cited before). Like I said, the media could provide a relatively high baseline and proximity is just augmenting that.

    Also, the relationship could also be based less on physical proximity and more on with relative proximity. Within a densely populated community it may be hard to distinguish between the two. Smaller communities may have entirely different networks of interaction that would allow information to spread in a similar manner. I grew up in a rural community, and I could see how a hub (like a school or church) would be a substitute for close neighbors when it comes to dissemination of information.

  45. joseph449008 says:

    @pD:

    My son has autism, but I can tell you without a doubt that I knew zero children with autism before my son was diagnosed, 1 kilometer from my home, or 100.

    Note that the authors did not say proximity to diagnosed children explains *all* diagnoses of autistic children. It’s basically just one mechanism they’ve demonstrated works. Other possible “awareness” mechanisms could be, for example, availability of information on the internet and the media, pediatrician knowledge, etc.

  46. joseph449008 says:

    If the TV and Internet aren’t good at raising awareness, and the spatial effect really is that strong, shouldn’t the rates of diagnosis be much lower in my area, where people are spatially distributed in much higher areas?

    Actually, low population density has a strong logarithmic association with the IDEA prevalence in California counties. Your area might be unique for other reasons, e.g. socio-economic status. Tell me, how did you first find out your son is autistic? Self-research, a really knowledgeable pediatrician, or a really expensive specialist?

  47. Todd W. says:

    @pD

    But look how steeply the effect drops off after only 250 meters in this study, again at 500 meters, and steadily declines.

    This is just conjecture on my part, but my guess is that the closer people live together, the more likely they are to talk and get to know one another. In other words, you are more likely to talk to your next-door neighbors than you are to talk to the family five or six houses down.

    As to TV or internet, why would it lead to a decrease in the proximity effect? I could see it augmenting the effect. Think of it like this: your neighbor sees something about autism on TV or reads something on the internet. They are intrigued and investigate further to the point they are convinced that their child might have autism. They find out through the same sources that there is a doctor nearby that can diagnose it. They take their child there and, lo and behold, the child has autism. This is big news. Because the signs were a bit more subtle until they investigated, they wonder if their friends and neighbors’ kids might be autistic. And so they share what they have found out.

    What does this mean to my community, where spatial differences can’t be having such wide ranging effects, but none the less, we are also experiencing widespread rises in autism diagnosis?

    Keep in mind that the researchers are not claiming that the proximity effect is the only or the largest risk factor for an autism diagnosis. You already said that in your community, an outreach program was undertaken. In your case, the proximity effect, as described in this paper, probably were not a significant factor, but the hunting for autistic kids was the primary risk factor. I’d be curious to know what the error rate of diagnosis was for that program; how many misdiagnoses have there been? Were the people behind it so intent on finding cases of autism that they found it even in children who were not autistic?

  48. # Todd W. – But look how steeply the effect drops off after only 250 meters in this study, again at 500 meters, and steadily declines.

    “This is just conjecture on my part, but my guess is that the closer people live together, the more likely they are to talk and get to know one another. In other words, you are more likely to talk to your next-door neighbors than you are to talk to the family five or six houses down.”

    This is also conjecture, but in my experience I am more likely to talk to others in the neighborhood who have children (my children’s age or babysitting age:). Also, I talk to others in our area who walk to pick up their children after school, so close proximity to school and children not in after school care. Also I talk to other waiting room parents (waiting for doctor’s appointment, waiting for speech pathology appointment, waiting for preschool speech therapy appointment.) About half those appointments are about 1/2 drive away, with other’s coming 1/2 away in other directions.

  49. provaxmom says:

    Was race/ethnicity accounted for? I just wonder if it would be the same for non-white, English speaking communities. My school district has about a 20% Mexican population, I wonder if 20% of the ASD Dx kids in our district are also Mexican. During some of the particularly trying times in advocating for my son (aka fighting for services) I often wonder if the kids of Spanish-speaking parents get left behind, because the parents can’t advocate for them as well. I wonder if the same holds true in pursuing a Dx.

    I have many non-white, non-English speaking neighbors, but we do not communicate more than smiles and nods when we’re out with our kids. Same for the pediatrician’s office–but the entire staff is bilingual.

    Just thinking out loud.

  50. marc says:

    I just read up on Kim Peek on Wikipedia, and that lack of corpus callosum stood out for me as well. Probably explains how he was able to read two pages at once, the left eye reading the left page and the right eye reading the right page. I guess my question as a non-neurologist would be: wouldn’t an ability like this lead to a diagnosis of lack of corpus callosum sort of automatically?

  51. passionlessDrone says:

    @milkerrattlesnake

    That the rates are rising in both areas is not in contention, but when you state that they are rising at the same rate I wonder what you are basing that on (maybe I’m forgetting a statistic you have cited before).

    I haven’t cited it; but even if something was available for our city I’d doubt it had much power. After all, the entire concept behind an almost completely artifact driven increase is the worthlessness of previous counting efforts. The problem I’m having is the very, very strong power being assigned to proximity factor. Living in an apartment building with a hundred other families ought to be a giant, huge risk factor. And while I have none of those in my city, we have lots of kids with a diagnosis.

    Also, the relationship could also be based less on physical proximity and more on with relative proximity. Within a densely populated community it may be hard to distinguish between the two.

    OK. But that tends to go against the conclusions of the paper:

    We observe a strong positive effect of proximity to other children with autism on the subsequent chance of diagnosis, robust to a range of individual‐ and community‐level controls in both urban and less urban areas.

    Your point concerning relative networks is valid, but then we are on our way to these findings being an artifact, and once again the god of the gaps argument of social constructs can be used to fill in whatever observed increases make us feel comfortable. This is possible, but I hate using it as a crutch, I think the question is just too important to leave up to softness of social sciences. Again, bioinformatics will one day tell us the answer.

    @ Joseph449008

    Tell me, how did you first find out your son is autistic? Self-research, a really knowledgeable pediatrician, or a really expensive specialist?

    The CARD center in our city had sent development analysis forms to all pediatricians in our city asking for us to help fill them out. He was flagged at the one we filled out at twelve months, tested subsequently at thirteen, eighteen, twenty four, and thirty six months.

    Actually, low population density has a strong logarithmic association with the IDEA prevalence in California counties. Your area might be unique for other reasons, e.g. socio-economic status.

    If I understand correctly, this would speak towards an urban effect, which to some extent corresponds to a spatial proximity effect. It just doesn’t seem like in an area the size of central LA we should see such drastic drop offs, but I dunno. (?) Further compounding this problem are a few recent studies concerning apparent clusters in the same area; they also pointed towards social (availability) issues driving diagnosis, but the risks seem to follow socio-economic lines, as opposed to distances. Any link seems to earn you moderation here; try googling autism cluster MIND california and you should get it.

    And I don’t really live in a rural environment, just a city mostly looks like a suburb compared to central los angeles. There’s plenty of people, you just have to drive a car to get anywhere meaningful. And that’s where this analysis is falling apart for me; the authors count on relatively short distances to focal points such as parks or pediatricians:

    Focal meeting points can typically be found within one to two kilometers in California: the median distance to the nearest playground or local park or preschool is 0.7 kilometers, and the distance to the nearest pediatrician is 1.1 kilometers (see table 1). Given the spatial structuring of interactions, if information about autism is flowing through interpersonal networks, close proximity to a child with autism should increase the likelihood of information diffusion (Rogers 2003).

    @Todd W –

    This is just conjecture on my part, but my guess is that the closer people live together, the more likely they are to talk and get to know one another. In other words, you are more likely to talk to your next-door neighbors than you are to talk to the family five or six houses down.

    OK. But if our very intense power of proximity is real, and dissapears once we move to less dense areas, shouldn’t we see a corresponding very drastic decrease in autism rates?

    As to TV or internet, why would it lead to a decrease in the proximity effect? I could see it augmenting the effect.

    OK, but look at the power of close proximity displayed; a 42% increased risk of a diagnosis if another child is diagnosed within 250 meters. Where has all of that power gone once we leave central los angeles?

    Keep in mind that the researchers are not claiming that the proximity effect is the only or the largest risk factor for an autism diagnosis. You already said that in your community, an outreach program was undertaken. In your case, the proximity effect, as described in this paper, probably were not a significant factor, but the hunting for autistic kids was the primary risk factor

    Agreed. But don’t we still have to contend with the fact that some areas should have far, far more powerful forces acting towards autism diagnosis than others?

    More tomorrow maybe. Thanks guys.

    - pD

  52. joseph449008 says:

    The CARD center in our city had sent development analysis forms to all pediatricians in our city asking for us to help fill them out. He was flagged at the one we filled out at twelve months, tested subsequently at thirteen, eighteen, twenty four, and thirty six months.

    So pD, in your case we’re talking about an “availability of specialist services” type of effect. Note that the authors never claimed *all* diagnoses are due to proximity to an already diagnosed child. That’s only one possible “awareness” mechanism. There are others, and I can speculate on those, e.g. having a coworker with an autistic child, internet searches, etc. BTW, you might be interested in a couple of Bass Diffusion models I derived to explain the 6-9 CalDDS prevalence.

    If I understand correctly, this would speak towards an urban effect, which to some extent corresponds to a spatial proximity effect. It just doesn’t seem like in an area the size of central LA we should see such drastic drop offs, but I dunno.

    Is the study of Central LA only? It doesn’t look like it is, so we can’t say if it applies or not to the LA area. It might not. In fact, the LA area has the highest administrative prevalence of the state, by far. It’s quite possible that proximity to specialist services trumps other factors there.

  53. passionlessDrone says:

    Hi Joseph –

    I was wondering if that was you or not. I guess Joseph@wordpress got taken a while ago. :)

    Note that the authors never claimed *all* diagnoses are due to proximity to an already diagnosed child. That’s only one possible “awareness” mechanism. There are others, and I can speculate on those, e.g. having a coworker with an autistic child, internet searches, etc.

    Of course, but that is still what is driving me crazy about the numbers; the proximity issue seems to be very, very powerful; even when the other mechanisms you list should still be in force.

    For example, everyone who works with me, everyone knows the signs of an autistic child at eighteen months, 2 years, 3 years, six years, nine months, and seveteen days, ect. None of them live within four miles of me, and most live far more than that [none, so far, have children on the spectrum]. Similarly, no one in my group of autism friends lives within 1 km of a pediatrician or a park. In our case, it would appear that spatial proximity has been superseded by other means, why would those other means be so fallible in this study?

    Is the study of Central LA only? It doesn’t look like it is, so we can’t say if it applies or not to the LA area. It might not.

    Well, maybe you have a point there. I read this:

    In the epicenter of our study area—Los Angeles, California—the vast majority (85%) of adults define their neighborhood to be an area that is within a 15‐minute walk from home (approximately one kilometer to 0.68 miles), and having children is negatively associated with the size of the neighborhood reported (Sastry, Pebley, and Zonta 2002).

    How far they expand their bubble, I haven’t been able to discern. (?)

    In fact, the LA area has the highest administrative prevalence of the state, by far. It’s quite possible that proximity to specialist services trumps other factors there.

    I tend to like this possibility a bit more than spatial proximity to another child with a diagnosis, as it allows for some of the other possibilities described above.

    I will try to get through the Bass Diffusion model post sometime when I can allocate a little more time.

    - pD

  54. joseph449008 says:

    @pD: In any CalDDS study, LA is going to be the “epicenter.” But it doesn’t necessarily mean the results are representative of what goes on in LA only.

    In our case, it would appear that spatial proximity has been superseded by other means, why would those other means be so fallible in this study?

    This study doesn’t look at other means of “information diffusion” like family or coworkers, as far as I can tell.

  55. chaoticidealism says:

    You mentioned epidemiology–the way an infectious disease spreads. Autism, of course, isn’t infectious; but the principles of epidemiology aren’t just valid for infectious disease. Or disease of any sort.

    Ideas spread the same way disease spreads. Fashion trends; Internet memes; gossip.

    I think there’s probably a doctoral project in it for someone–the idea of autism itself, spreading very much like this, with the same shape.

    The trend in autism diagnosis does look very much like the curves you see for the case numbers during a flu season…

  56. joseph449008 says:

    The trend in autism diagnosis does look very much like the curves you see for the case numbers during a flu season…

    Not really. That’s a sinusoid. The autism curves look quasi-logistic (or they will eventually.) I’m pretty sure one day it will be widely recognized that they fit a Bass Diffusion Model (which is used in marketing.)

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