Friday, April 03, 2009

Autism Awareness and its Relationship to the "Epidemic"

Yesterday was World Autism Awareness Day. (That's right, its acronym is WAAD, and it's the day after April Fool's day.) Given the occasion, I thought I would discuss "awareness." More specifically, I wanted to discuss how we can tell that awareness has had an impact in what is usually referred to as the "autism epidemic."

That awareness could account for much of the increase in autism diagnoses since the early 1990s is taken for granted. You will find awareness mentioned in many autism papers. In the recent MIND Institute paper (Hertz-Picciotto et al. 2008) awareness was acknowledged but not taken into account in the calculations. While H-P et al. apparently did not believe awareness to be an important factor, many other researchers seem to think it is. I personally believe it's supremely important. Changes in criteria can't in themselves cause the number of diagnoses to rise. Autistic persons need to be found and diagnosed (with autism) before they are counted. If diagnostic substitution is increasingly occurring, there's probably a reason why it's occurring: awareness.

Nevertheless, as far as I know, no one has ever demonstrated that awareness explains the rise, statistically. Thus, we fall into the same trap that proponents of most environmental hypotheses fall into. We assume that because awareness has increased in the information age (as it obviously must have) and rates of autism have also increased, one causes the other. Could it simply be a coincidence?

How do you measure awareness? Here's one way. I will use Google News Archive Search to search for the phrase "autism california" every year from 1992 to 2006. I propose that the number of results is an adequate proxy of autism awareness in California, though like all proxies, it's just an approximation.

I'd like to have data on diagnoses of autism to be able to make a comparison. I don't have that, however. Here's the next best thing. I will use data on number of California DDS clients with a classification of autism as reported on March of every year from 1993 to 2007. More specifically, I selected the number of autistic children born only 3 years prior to the report.

Let me explain the rationale. If we were to choose 5 year olds, that wouldn't work very well, as they could've been diagnosed when they were 2, 3, 4 or 5. It would be difficult to correlate caseload in the report year with awareness in several prior years. If we instead choose children born only 3 years before the report year, they almost necessarily have to have been diagnosed the year prior to the report year. This is especially true if we use the March report. If we were to use the December report, this again might not work very well.

Without further ado, the following is the graph I came up with.

The blue line represents awareness. The green line represents autism caseload of 3 year olds, approximately. There are 2 Y axis scales, left and right respectively. I think the 1 year lag between one and the other is pretty clear. If you prefer to visualize the data in a scatter chart, here it is:

It's true that correlations that are purely coincidental (e.g. pirates vs. global warming) can result in convincing scatter charts like the one above, and I haven't done further statistical analysis to rule out coincidence, but I think there are a couple of clear features of the series that make me think we're looking at causation. First, I already noted there's a 1-year lag in the expected direction. Second, awareness seems to start to shoot up in 1999. Autism caseload, in this cohort of very young children, starts to increase noticeably in 2000. Then there's also a clear spike in awareness in 2005, which corresponds to a spike in caseload in 2006.

Considering there's also plausibility, I think we can safely say awareness did have an impact in the rise of autism diagnoses. I only looked at very early diagnoses, but this is because I don't think I have other data that could be adequately used instead. I would imagine awareness has an impact on diagnoses at any age.


  1. You must enjoy doing statistical correlations, I don't

    However here is another one I made up on the spot you might like to check out.

    That there is a particular curve that relates to the propogation of every new diagnosis, that is dependant upon the media by which the message is transmitted, however mathematically, there will be a relationship whatever the media, that is there will be a specific rate of change that can correlate whilst the actual magnitudes will vary according to "bandwidth" eg, gutenburgs galaxy will show a similar exponential growth to Tim Berner's Lees.

    It follows that at first any knew knowlege is confined to a few, and it takes time for it to penetrate and disseminate. This is a media and a sociological phenomenon, related to communication theory, but no less scientific for that.

    Which again points out the advantage of syncretism, a scientist who has little grounding outside of the narrow confines of xyr particular discipline, rarely can step back and see what "universal laws" govern xyr own behaviour.

  2. I think what you're talking about is growth due to word of mouth, right Larry?

    Growth due to word of mouth is exponential, until there's saturation. It looks like this or this or this.

    Growth of the diagnosed autistic population is very similar. The growth pattern is what it should be if it is due to availability of information. If it were growth due to an environmental factor that is introduced at discrete times, I think you'd see something different.

  3. An interesting approach Joseph. There would seem to be lots of potential confounders (increased internet use/google popularity, trends towards earlier diagnosis, etc.), but this is interesting. I wonder how future reasearchers will attempt to quantify awareness and recognition.

  4. The internet no doubt has to do with it - the timing is just right - but the internet is just the medium. How the internet was used is probably a lot more complicated to quantify.

  5. I think awareness is key to the increase in autism diagnosis. Our son was diagnosed with Asperger's Syndrome in November of last year. He seems awfully normal to me- for a boy born into my family.

    Back when I was going to school we didn't hear much about autism or spectrum disorders. We still had kids like my son in our school- we called them computer nerds.

    I have at least one aunt and two uncles on my father's side of the family that would probably meet the criteria for AS diagnosis if they wished to be tested. Those 3 individuals comprise 30% of my father's generation.

    My generation has it's share of quirky individuals- interestingly, every male in my generation is an engineer. The females are market researchers, economists, bank loan officers, scientists, stay at home moms, and one cousin is pursuing a PhD in something to do with nanotechnoligies and nuclear applications. Our family (big Catholic family) is not normal by most standards. They haven't been normal for generations. They do excell in their careers and their lives.

    I think we've been selecting for autistic traits for generations. With an increase in awareness of autism spectrum disorders more people in my family are being classified as "disordered." In many ways I wish my son had never been tested. It's interesting to have an explanation for why he has a difficult time filtering some external stimuli. He's really no different from several other males in our family who are quite successful. I think the diagnosis may hold him back and make him less confident. It's not necessarily a great character trait but my family members have always coped by becoming arrogant.They always had very high intelligence and therefore concluded they were smarter than most of the rest of the world- why would they want to fit in?

    Sorry to take up so much space in your comments. I think you're doing a great service with your blog and can't wait to read more about your research and observations. It's become one of my goals in life to try and get people to look at Asperger's Syndrome in families like mine as more of a personality type and thought process than a disorder.

  6. No attempt to find out which variable on the graphs is independent and which one is the dependent variable?

  7. The 3 y/o caseload lags news reports by 1 year. So what do you think that means?

  8. "No attempt to find out which variable on the graphs is independent and which one is the dependent variable?"

    Jake.... you can't tell which is the dependent variable and the independent variable on a graph?!?!

    This is something you learn at comprehensive/grade school!

    It is something that is laid down in convention on displaying statistical information!

    And you ask THAT question? I could tell identify IV and DV by at least the third or fourth week of my OND course in Technology... and that was the balancing period; I taught school-level mathematics for those retaking the subject - and I'm pretty damn sure we talked about IV and DV when we were dealing with the topic of drawing graphs.

    If you're on about the quantities forming these things... on the graphs in Joseph's blog article.. they are actually named on the graphs. This isn't rocket science...

  9. See the following theory:
    The ‘theory of mind’ (ToM) hypothesis of autism. Tom is an hypothesis first published in 1985.
    Other articles ask what caused the autism epidemic?
    The CDC studies say it is not MMR or Thimerosal. Other hypotheses have included autoimmune diseases, etc.

    Individuals with Disabilities Education Act (IDEA) Data website:
    Pregnancy Risk Assessment Monitoring System (PRAMS) sleep position data:
    Centers for Disease Control (CDC) Birth Data:
    2006 Median Income Data: - U.S. Department of Housing and Urban Development
    NOTICE PDR-2006-01

    Autism Spectrum Disorders, Asperger's Syndrome, and Pervasive Developmental Disorders - Not Otherwise specified (PDD-NOS)
    Gastrointestinal Disorders also known as GER is a common comorbidity
    Autism patients tend to have minicolumn abnormalities and increased amounts of white matter
    Casanova MF, van Kooten IA, Switala AE, Ven Engeland H, Heinsen H, Steinbusch HW, Hof PR, Trippe J, Stone J, Schmitz C. Minicolumnar abnormalities in autism. Acta Neuropathol. 2006 Sep; 112(3); 287-303.
    Mostofsky SH, Burgess MP, Larson JCG. Increased motor cortex white matter volume predicts motor impairment in autism. Brain (2007), 130, 2117-2122

    Maternal smoking decreased significantly between 1990 and 2002
    Infant suffocation deaths increased 14% per year on average between 1996 and 2004
    Centers for Disease Control. Smoking & Tobacco Use - Morbidity and Mortality Weekly Reports (MMWRs) – Smoking During Pregnancy – United States, 1990-2002 – October 7, 2004 / Vol. 53/ No. 39
    Shapiro-Mendoza CK, Kimball M, Tomashek KM, Anderson RN, Blanding S.US Infant Mortality Trends Attributable to Accidental Suffocation and Strangulation in Bed From 1984 Through 2004: Are Rates Increasing? Pediatrics 2009;123;533-539

    Here is a good article on diagnosing this:
    Filipek P, Accardo P, Ashwal S, Baranek G, Cook E, Dawson G, Gordon B, Gravel J, Johnson C, Kallen R, Levy S, Minshew N, Ozonoff S, Prizant B, Rapin I, Rogers S, Stone W, Teplin S, Tuchman R, Volkmar F. Practice parameter: Screening and diagnosis of autism Report of the Quality Standards Subcommittee of the American Academy of Neurology and the Child Neurology Society NEUROLOGY 2000;55:468–479

    SIDS, Autism, Autism Spectrum Disorder, Plagiocephaly, etc. are all
    conditions that the medical profession is trying to treat.
    The SIDS back sleep (Supine) sleep recommendations began in 1992
    The SIDS "Back to Sleep" campaign began in 1994.
    In 1996 the AAP SIDS Task Force, led by Dr. John Kattwinkel recommended the supine sleep position and not the side(lateral) or front(prone).
    THe Netherlands began their SIDS Back to Sleep Campaign in 1987.
    Sleep is necessary for memory consolidation, declarative learning, and procedural learning.

    The following are useful articles which discuss many of these issues indepth:
    American Academy of Pediatrics Task Force on Infant Positioning and SIDS. Positioning and SIDS. Pediatrics. 1992;89:1120-1126
    Hogberg U, Bergstrom E. Suffocated Prone: The Iatrogenic Tragedy of SIDS. American Journal of Public Health. 2000;90:527-531
    National Infant Sleep Position Household Survey. Summary Data. updated: 10/16/08 Website:
    Kattwinkel J, Hauck F.R., Moon R.Y., Malloy M and Willinger M Infant Death Syndrome: In Reply, Bed Sharing With Unimpaired Parents Is Not an Important Risk for Sudden. Pediatrics 2006;117;994-996
    Buzs├íki, G. 1989. Two-stage model of memory trace formation: A role for “noisy” brain states. Neuroscience 31: 551–570.
    Hasselmo, M.E. 1999. Neuromodulation: Acetylcholine and memory consolidation. Trends Cogn. Sci. 3: 351–359.
    Wierzynski DM, Lubenov EV, Gu M, Siapas AG. State-Dependent Spike-Timing Relationships between Hippocampal and Prefrontal Circuits during Sleep. Neuron 61, 587-596, February 26, 2009
    Walker MP, Stickgold R. Sleep, Memory, and Plasticity. Annu. Rev. Psychol. 2006. 57: 139-66
    Gais S, Born J. Declarative memory consolidation: Mechanisms acting during human sleep. Learn Mem. 2004 Nov-Dec; 11(6): 679-685
    Davis BE, Moon RY, Sachs HC, Ottolini MC. Effects of sleep position on infant motor development. Pediatrics. 1998 Nov; 102(5):1135-40.
    Skadberg BT, Markestad T. Consequences of Getting the Head Covered During Sleep in Infancy. Pediatrics 1997;100;e6
    AJ Williams, RD Jitendra, JB Phillips, Y Lin, T McCabe, FC Tortella. Neuroprotective Efficacy and Therapeutic Window of the High-Affinity N-Methyl-D-aspartate Antagonist Conantokin-G: In Vitro (Primary Cerebellar Neurons) and In Vivo (Rat Model of Transient Focal Brain Ischemia) Studies1
    Stradling JR, Thomas G, Warley AR, Williams P, Freeland A. Effect of adenotonsillectomy on nocturnal hypoxaemia, sleep disturbance, and symptoms in snoring children. Lancet. 1990;335 :249 –253

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