Autism research in 2023: a bit of a game-changing year

 So, autism research in 2023. It’s been quite a year. Let me (briefly) tell you why.

The autism numbers game: the only way is (still) up. Northern Ireland, where some great work is done to plot the annual (estimated) prevalence rate of autism spectrum disorder (ASD) in school-aged children, said 1 in 20 (or 5%) in 2023. The US CDC said an estimated 1 in 36 8-year olds (2.7%) were autistic in 2020. The CDC also said 1 in 47 4-year olds were autistic (2%). Scotland also recently produced data observing “The prevalence of autism was 2.60% (10,089 children) in 2022. This represents a 31.98% increase from the 2018 prevalence of 1.97% (7883 children).” That Scottish data, by the way, only covered those at primary school (aged 4ish-12ish years). Other sources too are still showing a growth in the prevalence of autism across other parts of the globe, including a near 5% rate of behaviours consistent with autism or ASD in the Hadza of Tanzania. All data on autism prevalence is still only heading in one direction: UP. 

Importantly, the old ‘all better awareness’ arguments are slowly fizzling out as the effects of those prevalence stats are starting to show on resources and infrastructure that seemingly haven’t kept pace with the growth in numbers. Indeed, one of the head people related to the CDC autism figures, went as far as to say that the stats don’t really support ‘better awareness’ as the primary driver given that the increase is showing across various different ‘levels’ of autism that are/were unlikely to be missed or thought to be something else. Certainly here in the UK, I don’t think I’ve ever read so many reports about school place shortages (particularly specialised school place shortages) as I have this year. And unfortunately, with an estimated 140,000 people (mostly children and young people) awaiting assessment in England alone, I fear the squeeze on resources is just going to get worse and worse. Anyone care to start asking ‘why the increase’ yet?

CDC says yes to ‘profound autism’. Speaking of autism ‘levels’ (as in DSM-5 autism levels of support or the ICD-11 condition combinations), the CDC did something else rather important this year: producing the first ever report on the rate of profound autism in the US. So, for data covering the years 2000-2016, and using the descriptor “classified as having profound autism if they were nonverbal, were minimally verbal, or had an intelligence quotient <50” they determined that 26.7% of those with autism fitted into the profound autism category. An estimated quarter of autistic people are profoundly autistic. That’s quite important.

There were mixed reactions to the CDC use of the term profound autism. Many people were happy to see it, given that it now lays the foundations for more research and more understanding that despite being united by a triad/dyad of symptom combinations, not everyone experiences autism in the same way. Look no further than the awful early mortality statistics following the deadly triad that is autism, wandering/elopement and water safety to see this in action. Of course autism by virtue of just being diagnosed, means support is required for everyone with the diagnosis. But that support will arguably differ depending on whether you possess things like communicative speech and language, present with things like self-injurious or aggressive behaviours and/or need 24-7 care to ensure that your daily needs are fulfilled. Indeed, I often think that the general lack of support post autism diagnosis is a big driver in the reticence to adopt the term profound autism in some quarters. But should people be so reticent? I mean we have similar distinctions when it comes to experiences of learning (intellectual) disability and nobody seemingly bats an eyelid there. 

There is however more to do on profound autism. This ties into other changes that are needed when it comes to assessing things like cognitive functions and communication (verbal or non-verbal) ability in relation to autism. That’ll follow as the term beds in and builds up more of a research base. Asperger syndrome gone, profound autism steps in.

What else? 

Non-persistence of autism in (some) young kids. 2023 also gave a lot more credence to the idea that the saying ‘all autism is lifelong’ probably isn’t as accurate as you might think. Looking at the developmental trajectories of around 200 kids, all diagnosed early with autism, saw about a third of them not continuing to meet the diagnostic threshold for autism/ASD at ages 5-7 years according to a big study. Other independent work also illuminated this topic and argued against the ‘just misdiagnosed’ suggestions that some people might make and that also the state of ‘autism free’ might have important implications for various other issues too.

This was a particularly important finding for me given our paper from a few years back talking about inborn and lifelong not necessarily being the most accurate phrases for all autism. It also accords with various other studies in related areas observing that diagnoses like ADHD and depression for example, aren’t lifelong labels for absolutely everyone either. Although I noted some people tried to talk about ‘masking’ and ‘camouflaging’ as being the reasons why young kids in that JAMA study didn’t meet the thresholds for autism having previously done so, I do have to ask whether they’ve ever seen autistic kids at this age. Indeed, any child at this age, who generally aren’t renowned for their developed social etiquette abilities covering masking et al (this is also the reason that the gold-standard autism assessment instrument, the ADI-R, codes 4-5 years separately from ‘current behaviour’). As to why autism doesn’t persist for some, well, we don’t know exactly. There was talk of intervention potentially playing a role (behavioural intervention) but it’s probably going to be a bit more complicated than just that. For now, we await further studies on this important topic including more longitudinal ones and perhaps also looking at the biology behind this phenomenon. If I was to speculate about why there is autism non-persistence for some, I might be inclined to say ‘look to infection’ for some, and how, more and more, we’re learning that infection and immune responses to infection can manifest as behaviour and developmental issues as well as in immune biology. Just me speculating, so pay no mind (although that autism in Hadza children study did nicely reignite my interest in how infections like malaria can, through various mechanisms, also seemingly lead to autism).

The gut-brain axis is important to autism. I know a lot of people already appreciate this, but seeing it in a peer-reviewed mega paper in 2023 adds a lot more weight to it. Said paper trawled through huge amounts of data about gut bacteria and the like, and concluded that there is something to see both as observation and also as potential intervention. Authors even mentioned the words ‘faecal matter transplant’ (FMT) in the context that what goes on in the gut doesn’t necessarily stay in the gut, and something that is rising in some autism research and other circles. Allied to the gut-brain axis stuff was the reporting from other mega review papers observing that gastrointestinal (GI) symptoms are present in roughly 55% of children with autism, compared with about a quarter of non-autistic children. Constipation comes out on top. So fixed to clinical advice about treating such issues published over 10 years ago, maybe now is the time to preferentially screen and treat such issues in the context of autism? Perhaps recognise that the gut and brain are connected for quite a few labels/conditions? More on that shortly.

Various medical issues are over-represented in autism. More important data points to the various clusters of medical (somatic) issues that seem to accompany autism across the age ranges. Ranging from cardiovascular conditions to immune-mediated conditions, various studies confirmed what quite a few people already knew. With my gluten research hat on (I don’t actually have a hat made of gluten), I was glad to see that the archetypal gluten-related autoimmune condition called coeliac disease was given mention. Who knows, between coeliac disease and the slightly greyish area of non-coeliac gluten issues that seem to be over-represented alongside autism, there’s further hope for wider screening and use of a gluten-free diet in the context of autism? Oh, and just before you inquire about the research base in this area, here’s a couple of meta-analyses from the last few years - see here and see here - saying it might be worth a shot (minus any clinical or medical advice given or intended).

And there was yet more research on the psychiatric and behavioural issues that seem to be over-represented alongside autism. Importantly, and I do think needs a lot more investigation, one study out of Canada stressed the need to look at comorbid psychiatric issues as being an important driver of suicidal behaviours in the context of autism. I know such behaviours are complex and often very individual with a heavy biopsychosocial tilt, but there’s a wealth of evidence out there already suggesting that depression, bipolar disorder, personality disorder and schizophrenia spectrum disorders all convey a heightened risk for suicidal behaviours. All those conditions are well over-represented alongside a diagnosis of autism (yep, an estimated 1 in 10 autistic people will potentially ‘transition’ to schizophrenia). Screen, screen and treat (including, where appropriate, more clinical emphasis on the archetypal anti-suicidal agent that is lithium used in the right context).

Late 2023 research entry: CM-AT results are really, really, really promising. I’ve been following the CM-AT story for quite a while on this blog and beyond. Basically, it concerns a pancreatic enzyme therapy designed for autism that has already crossed quite a few methodological trial hurdles. Then, in November 2023 lo and behold, the results of a double-blind, placebo-controlled trial that say, yes, following the gold-standard trial design, CM-AT is good for treating/managing irritability and agitation in the context of autism in pre-schoolers. Said treatment is also likely safe and effective. This is a potential game-changer and opens the door to things like regulatory approval. Also, exquisite evidence for the whole ‘behaviour is biology’ tenet and the important role of the gut-brain axis in autism, yet again.

There was so much more other science published this year, across all-manner of different topics. Certainly far too much for me to put into one blogpost. I’m a great believer in your citizen scientists and so would encourage everyone to look-see and take part. I can’t help but draw your attention to another paper that basically said the ‘person with autism’ vs ‘autistic person’ arguments typically seen on social media aren’t really worth a dime. Ask the person how they want to be addressed. Oh, and remember, people aren’t ‘neurotypes’ either. They’re people. 

And finally… Saying farewell to Donald.

Finally, [I can see you’re yawning] a non-sciency thing to mention. ‘Patient 1’ from the great Leo Kanner’s seminal paper describing autism - Donald Triplett - passed away. If you’ve ever read or watched ‘In a Different Key’ you’ll have read about him or seen him. Of all the things said about Donald in the various obituaries to him, I think the overwhelming idea that comes across is how much community was important to him; both being part of a supportive community and having a great community around him. Loads of lessons to be learned there. My advice: seek out those who wish to foster community, and there are lots of good people of this ilk. Here's to 2024 and beyond.

Iceberg! Have we reached a tipping point in autism numbers and assessment referrals?

Sorry. I really am. I'm back at the autism research blogging yet again, twice in a week. I know some people will be unhappy about that (I can hear the Twitterer cries already: 'keep yer bloody mouth shut!') but hopefully some won't be so unhappy. But writing this on a nice sunny March Sunday evening with a rerun of Titanic playing on the telly, I'm gonna talk about whether or not we've just hit the iceberg when it comes to US autism (estimated) prevalence (and those from elsewhere) and the huge backlog of autism referrals that's been making news here in Blighty aka dear old England. I'll also come clean and mention that I actually do like the film Titanic. There I said it. 

I appreciate that my use of the word 'iceberg' in the context of this blog is not likely to sit well with some people. How dare I talk about icebergs in the context of autism prevalence and such like? Well, I dare because right now there's a lot of people who are genuinely concerned that more than ever we might have started to head into and indeed, already started to scrape past, an iceberg that's been on the horizon for a number of years. And in the current climate of post-pandemic financial and resource pressures, we haven't exactly got the strongest of hulls in this societal ship in which we're all passengers on. 

So, last week we had the estimated autism prevalence figures for 8-year olds in the United States from the CDC (see here). Actually we had another set of (estimated) figures relating to 4-year olds too (see here). The headline figure: well, words like 'all-time high' have been used to cover the 1 in 36 8-year olds estimated to have autism or an autism spectrum disorder (ASD). As for 4-year olds, and as per other reports (see here), 1 in 47 4-year olds was the headline figure, a leap from previous reports for this age group (1 in 59 in 2018). Both sets of figures chart the estimated numbers of cases of childhood autism and illustrate the ever upward trend that we've been seeing over the past few decades in the US and beyond.

Most press coverage of the CDC data have not sugar-coated it. Yes, there's been talk about how racial disparities in screening and assessment have been reduced in the recent figures and that's a good thing. There's also talk about the (subtly) declining male:female ratio which again, represents good progress in detection and identification. But then the conversations move to the need to provide suitable services. Y'know things like education, social and health services, and this is where the tone gets a little more serious as per the realisation that there's probably not enough suitable or appropriate services for everyone, and what services there currently are, are probably going to become even more scarce as more people need them. As an aside it's interesting too that this time around, some discussions on the new CDC figures have basically poo-pooed the whole 'it's all better awareness' arguments: "This is not just a phenomenon of becoming more sensitive to subtly impaired kids" according to one very senior person intricately involved in the CDC process of autism counting. Progress indeed given the amount of times that argument has been used, fairly unscientifically, in the past.

On this side of the Pond, I think we're starting to really see that process of 'lack of suitable services' playing out in real time. We - the UK we - are still waiting for a truly national autism prevalence initiative but we have some good counting processes in place in relation to countries of the UK like Northern Ireland and their forward-thinking in collecting and publishing school-aged autism prevalence data (see here). Northern Ireland is, I think, due to report in a few weeks time but the last time around the prevalence of autism in school-aged children came it at 1 in 21 children (see here) or 4.7% of school-aged children with autism in 2021/2022. I also happened to stumble on some other, more England-based data recently (see here) that mentioned that "2.84% of 10-14-year olds were diagnosed (1 in 35)." Obviously, one has to be a little careful with that last statistic. What this means is that the latest CDC figures for the US are not an isolated incident. They're more likely part of a global trend where the old 1% prevalence figure is completely out of sight in the rear view mirror.

As to that 'lack of suitable services'? Loads of examples to pick from. Take for example the recent BBC news report (see here) on twins, yes twins, both diagnosed with autism (and dare I say autism heading more towards 'profound'), both with EHCPs (education and healthcare plans) yet one twin offered a place at a specialised setting, the other not. The reason: the specialised setting is 'over-subscribed'. Twins. There's loads more other examples like this. Such examples complemented (if that's the right word) by multiple reports of plans to build more and more specialised schools with seemingly little realisation that said schools take a while to be built and then also need to be suitably staffed, which leads us down another potential rabbit hole. Another aside: we have some of the best teaching cupboards (yes, you heard right) in the world here in England (see here).

And if you think things are critical when it comes to resources for those lucky enough to already have a diagnosis, spare a thought for the thousands and thousands of people - predominantly school-aged children - who are waiting just to get on a waiting list for autism assessment (see here). In England alone there's about 140,000 people waiting at the time of writing (see here), again predominantly school-aged children. And now another reality: one particular part of England has recently decided that the huge numbers of people, again predominately children, wanting an autism assessment will be 'triaged' to filter out 'the most needy' (see here). That's triage as in what's normally seen on the battlefield when care is rationed according to those most in need. So children now have to be 'in crisis' before they're put on a list for a referral for autism assessment. We've hit the iceberg, haven't we? 

I don't really know what else to say about all this. Yes, it's great that everyone is getting better at recognising autism. Yes, it's great that more people are being detected and referred for an assessment. We can pat ourselves on the back for that. Unfortunately, as a society we've had our collective heads buried in the sand about what rising numbers of need actually means. And now, it's having real-world implications for many people and their loved ones. 

How many lifeboats did you say we have?

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Maenner MJ, Warren Z, Williams AR, Amoakohene E, Bakian AV, Bilder DA, Durkin MS, Fitzgerald RT, Furnier SM, Hughes MM, Ladd-Acosta CM, McArthur D, Pas ET, Salinas A, Vehorn A, Williams S, Esler A, Grzybowski A, Hall-Lande J, Nguyen RHN, Pierce K, Zahorodny W, Hudson A, Hallas L, Mancilla KC, Patrick M, Shenouda J, Sidwell K, DiRienzo M, Gutierrez J, Spivey MH, Lopez M, Pettygrove S, Schwenk YD, Washington A, Shaw KA. Prevalence and Characteristics of Autism Spectrum Disorder Among Children Aged 8 Years - Autism and Developmental Disabilities Monitoring Network, 11 Sites, United States, 2020. MMWR Surveill Summ. 2023 Mar 24;72(2):1-14. doi: 10.15585/mmwr.ss7202a1. PMID: 36952288.

Shaw KA, Bilder DA, McArthur D, Williams AR, Amoakohene E, Bakian AV, Durkin MS, Fitzgerald RT, Furnier SM, Hughes MM, Pas ET, Salinas A, Warren Z, Williams S, Esler A, Grzybowski A, Ladd-Acosta CM, Patrick M, Zahorodny W, Green KK, Hall-Lande J, Lopez M, Mancilla KC, Nguyen RHN, Pierce K, Schwenk YD, Shenouda J, Sidwell K, Vehorn A, DiRienzo M, Gutierrez J, Hallas L, Hudson A, Spivey MH, Pettygrove S, Washington A, Maenner MJ. Early Identification of Autism Spectrum Disorder Among Children Aged 4 Years - Autism and Developmental Disabilities Monitoring Network, 11 Sites, United States, 2020. MMWR Surveill Summ. 2023 Mar 24;72(1):1-15. doi: 10.15585/mmwr.ss7201a1. PMID: 36952289.

Early Autism and Developmental Disabilities Monitoring says autism prevalence is still rising...

"The overall ASD [autism spectrum disorder] prevalence was 13.4 per 1,000 children aged 4 years in 2010, 15.3 in 2012, and 17.0 in 2014 for Early ADDM [Autism and Developmental Disabilities Monitoring] sites with data for the specific years."

So said the surveillance summary published by Deborah Christensen and colleagues [1]. Those of you who follow the US ADDM initiative (see here) will already know about the aims of this "group of programs funded by the CDC" looking at the (estimated) autism numbers, changes to the numbers and the impact of the numbers on various communities. Through initiatives like the ADDM, we already know that the estimated prevalence of autism in 8-year olds living in the United States is round about 1 in 59 (see here) and that the estimate continues to grow for pretty much every surveillance year examined. We are also starting to find out about how the change to DSM-5 from DSM-IV is likely to/not to impact on future figures (see here). And hopefully, at some point, we might have some further data on what happens to autism past childhood (see here) from such an initiative.

The Christensen paper adds another tier to the knowledge being acquired as per their analysis of the (estimated) prevalence rate of autism in 4 year olds "whose parents or guardians lived within designated sites." Those sites were: Arizona, Colorado, Missouri, New Jersey, North Carolina, Utah, and Wisconsin. The Early ADDM initiative does not cover the same area as its big brother/sister ADDM but "is conducted in two phases using the same methods and project staff members as the ADDM Network." Those phases include first "reviewing and abstracting data from children’s records, including comprehensive evaluations performed by community professionals" and then a second phase involving "a review of the abstracted evaluations by trained clinicians using a standardized case definition and method." DSM-IV criteria covers most of the time points examined but: "For 2014 only, prevalence estimates based on surveillance case definitions according to DSM-IV-TR and the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) were compared."

Results: as per the opening sentence of this post, the overall (estimated) autism prevalence across all sites for autism in 4 year olds was on the increase between 2010 and 2014. That's not to say that there weren't differences between the various sites - New Jersey, a favourite autism prevalence site (see here) showed the highest prevalence: 19.7, 22.1, and 28.4 per 1,000 for 2010, 2012 and 2014 respectively - but overall the prevalence rate was increasing not decreasing.

There were a number of other important points raised in the Christensen findings. So: "Among four sites with ≥60% data on cognitive test scores (Arizona, New Jersey, North Carolina, and Utah), the frequency of co-occurring intellectual disabilities was significantly higher among children aged 4 years than among those aged 8 years for each site in each surveillance year except Arizona in 2010." I don't think I need to say much more about that. Also: "The overall prevalence estimate using a DSM-IV-TR case definition was approximately 20% higher than the prevalence estimate based on DSM-5 criteria." Again, I don't think too much more discussion is needed on this point aside from saying that for 4-year olds, the switch to DSM-5 might have made more of a difference than for 8-year olds. Indeed in comparison to the Wiggins data [2] based on 8-year olds where "46.0% children met both DSM-IV-TR and DSM-5 surveillance status, 44.0% met neither the DSM-IV-TR nor DSM-5 surveillance status, 4.0% met DSM-IV-TR status, but not DSM-5 status, and 6.0% met DSM-5 status, but not DSM-IV-TR status of ASD" the Christensen data showed something a little different: "Among 1,237 children who met the surveillance case definition for either DSM-IV-TR or DSM-5, 974 (78.7%) met both case definitions, 234 (18.9%) met the DSM-IV-TR but not the DSM-5 case definition, and 29 (2.3%) met the DSM-5 but not the DSM-IV-TR case definition." Perhaps more study is required on the diagnostic changes?

What's more to say? Well, one of the authors - Walter Zahorodny - kinda said it all in a media comment: "There’s no letup. I really don’t understand why the rate is going up in this way." So maybe the next question, a question that really should have been examined a long, long time ago, needs to be 'Why?' rather than just a continual chain of studies saying autism prevalence is increasing...

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[1] Christensen DL. et al. Prevalence and Characteristics of Autism Spectrum Disorder Among Children Aged 4 Years - Early Autism and Developmental Disabilities Monitoring Network, Seven Sites, United States, 2010, 2012, and 2014. MMWR Surveill Summ. 2019 Apr 12;68(2):1-19.

[2] Wiggins L. et al. Comparison of autism spectrum disorder surveillance status based on two different diagnostic schemes: Findings from the Metropolitan Atlanta Developmental Disabilities Surveillance Program, 2012. PLoS ONE. 2018; 13(11): e0208079.

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Estimated one in 69 children aged 8 years old with autism (not one in 68) in 2012

"On June 5, 2018, the authors informed MMWR [Morbidity & Mortality Weekly Report] about a number of inadvertent errors throughout the report that resulted from reporting of autism spectrum disorder cases among persons who did not live in the geographic surveillance area."

So said a brief note [1] recently listed in the CDC Morbidity & Mortality Weekly Report (MMWR) concerning an important article published in 2016 [2] that described the estimated autism prevalence rate in the United States in 2012 for children aged 8 years old.

The original paper by Deborah Christensen and colleagues [2] was fodder for this blog at the time of publication (see here), with their estimated figures for 2012 (one in 68) showing a potential plateauing of the autism estimated prevalence rate in the US (see here for some discussion on the previous figures for 2010). The 'plateau' proved to be short-lived; as more recent figures published this year (2018) for the surveillance year 2014 once again showed the continuation of the upward trend (see here) in the childhood autism prevalence rate, now up to an estimated 1 in 59 children. Other figures have suggested even 1 in 59 is likely an understatement (see here).

Christensen and colleagues have republished their 2016 paper [3] showing 'where they went wrong'. It's not a wildly different article from their original publication and to a large extent, does not alter the underlying figures in any hugely significant way: 'one in 68' is replaced by 'one in 69'. Looking at the tables accompanying the Christensen republication, I was first drawn to Table 2 showing the: "Estimated prevalence* of autism spectrum disorder [ASD] among 1,000 children aged 8 years, by sex —Autism and Developmental Disabilities Monitoring Network, 11 Sites, United States, 2012." Under the column labelled "Total no. with ASD" it looks like a few participating States had corrections. Arkansas in particular stood out; their total going from 170 with ASD down to 125. Their estimated autism prevalence subsequently dropped from 12 per 1,000 children (aged 8) to 8.8 per 1,000. Other States showed a correction in the opposite direction. New Jersey (which has had an important role to play in the CDC estimates) showed a slight increase (of 3 children) in their "Total no. with ASD" similar also to Missouri.

There's little more to say about the Christensen correction aside from reiterating that: (a) the CDC statistics citing figures like 'one in 69' or more recently 'one in 59' are estimates, and (b) how and what data you include for counting is going to have an important bearing on what (estimated) prevalence rate you arrive at. By saying all that, I've not changed my view that we are witnessing something of at least a partial 'real' increase in cases of autism (see here and see here and see here) as older 'better awareness' and 'diagnostic substitution' arguments become less and less relevant as the numbers (estimated) climb ever higher. And aside from keeping on asking 'why?' the powers-that-be should be putting a lot more money and resources into the services that will inevitably be required, to ensure that children and adults on the autism spectrum aren't (societal) disadvantaged by their diagnosis.

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[1] No authors listed. Correction and Republication: Prevalence and Characteristics of Autism Spectrum Disorder Among Children Aged 8 Years - Autism and Developmental Disabilities Monitoring Network, 11 Sites, United States, 2012. MMWR Morb Mortal Wkly Rep. 2018 Nov 16;67(45):1279.

[2] Christensen DL. et al. Prevalence and Characteristics of Autism Spectrum Disorder Among Children Aged 8 Years--Autism and Developmental Disabilities Monitoring Network, 11 Sites, United States, 2012. MMWR Surveill Summ. 2016 Apr 1;65(3):1-23.

[3] Christensen DL. et al. PPrevalence and characteristics of autism spectrum disorder among children aged 8 years — Autism and Developmental Disabilities Monitoring Network, 11 sites, United States, 2012. MMWR Surveill Summ. 2018 Nov 16;65(13):1-23.

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"This goal is basically to find out what’s happened to these kids since age 8."

Credit: Disability Scoop 23 August 2018

It's another news report that provides the blogging fodder today, rather than a peer-reviewed science paper. No, this does not signify a significant shift in the aims and objectives of this blog away from peer-reviewed science material; rather I'm just commenting on something that might turn out to be quite important to the autism spectrum and will probably appear in the peer-reviewed science domain at some point. The news report in question (see here) is titled: CDC Expands Autism Monitoring Efforts.

CDC refers to the US Centers for Disease Control and Prevention, and the report is pertinent to their continuing efforts to chart the estimated prevalence of autism in the United States (see here and see here for some examples). This is done to a large extent via the Autism and Developmental Disabilities Monitoring Network (ADDM), with statistics based on the number of eight year olds estimated to be diagnosed with autism or an autism spectrum disorder (ASD). Why 8 year olds? Well, I assume it's because this is an age where autism will (*should*) be diagnosed and avoids any earlier years diagnostic confusion and the like.

But it appears that this initiative does not want to just remain focused on 8 year olds as we are told that: "the agency wants researchers at up to two sites to look at 16-year-olds who were previously identified as having autism symptoms in the network’s tracking when they were age 8." Further: "This goal is basically to find out what’s happened to these kids since age 8."

The rationale behind such a decision is a noble one. It's about looking at whether children diagnosed with autism/ASD "have other health conditions and what types of services they are receiving at school and otherwise." 'Other health conditions'? Erm, I'd hazard a guess and say yes, yes they will typically have some other health conditions (see here) also presenting. It's an agenda that also fits in well with the partial shift in focus from children on the autism spectrum towards teens and adults with autism. As for the 'services they are receiving at school' angle, well, this could also be important in terms of best practice too. I say that mindful of the fact that over here on the other side of the Pond, there has been some significant legal movement on schooling in the context of autism recently (see here).

But there is another aspect to such a decision by the CDC that might also be interesting to look at: that pertinent to the stability of an autism diagnosis (see here and see here for examples).

I know some people don't like to talk about the observation that autism, for some, is not necessarily a lifelong diagnosis (see here). The idea that within the huge heterogeneity included under the label of autism not everyone has a stable presentation across the lifespan is a jarring concept, particularly in the context that some people see their autism as so much more than just a diagnostic label. I hear words like 'masking' and 'camouflaging' being used more often to potentially explain why some people don't meet the diagnostic cut-offs for autism/ASD having previously done so. This may well apply to some people, but I don't think this represents an intellectually satisfying universal explanation for such a phenomenon and denigrates a potentially important finding. That also, 'losing a diagnosis' might impact on other issues 'over-represented' in relation to autism (see here and see here) provides further evidence for something other than masking potentially going on (unless the act of masking is somehow 'protective against' the likelihood of psychiatric comorbidity occurring alongside autism?)

I don't want to pre-empt any decisions from the CDC about their shift in focus and what they will and won't look at. Guaranteed that if such a proposal comes to being, the data will reveal something interesting and important, moving forward from just the autism 'numbers game'. If however, diagnostic stability does crop up as part-and-parcel of the new CDC autism prevalence agenda, I daresay that more research resources will be put into looking at the hows-and-whys of this issue. And perhaps too important areas like whether there are genetic and/or biological 'changes' associated with not subsequent fulfilling the diagnostic criteria for autism will also start to figure.

To close, I'm going to link again to the recent-ish findings from Bal and colleagues [1] suggesting that "some older adolescents and adults with ASD may not exhibit the same difficulties observed in young children with ASD" as a template for further study in this area. This, as part of a recognition, that "some will be largely free from symptoms of the disorder by adulthood" [2] (see here for my take) observed by some authors. Feathers will no doubt be ruffled.

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[1] Bal VH. et al. Autism spectrum disorder symptoms from ages 2 to 19 years: Implications for diagnosing adolescents and young adults. Autism Res. 2018 Aug 12.

[2] Lord C. et al. Autism spectrum disorder. Lancet. 2018 Aug 11;392(10146):508-520.

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'What really grinds my gears': a "slight uptick' in the estimated prevalence of autism

For those who watch the sometimes 'cutting' TV show called Family Guy, the first part of the title of today's post - "what really grinds my gears" - will make sense. For those who don't, it represents a TV segment offered to one of the main characters of the series, Peter Griffin, during which he aired increasingly bizarre opinions of things that 'irk' him. At the close, he revealed that just about everything 'grinds his gears'.

Whilst I'm not typically a person that is easily irked (much of my early years irking has dissipated as a result of age and my hobby), I was a little put out by the opening sentence included in the news piece published by Bridget Kuehn [1] talking about the most recent autism estimated prevalence figures published by the US CDC [2] (see here for my take). To quote: "A slight uptick in US cases of autism spectrum disorders (ASDs) was detected in 2014 compared with the years between 2010 and 2012, according to a new CDC report."

It was the use of the word 'slight' that furrowed my brow. And how a 15% increase in the estimated autism prevalence rate in the US over 2 years - translating as a move from an estimated 1 in 66 8-years olds being diagnosed to 1 in 59 8-years olds being diagnosed - is somehow inferred to be less important than it actually was. Words matter.

I know prevalence (and incidence) rates (estimated or actual) when it comes to autism can invoke some often heated discussions. Such debates perhaps tie into wider views held about autism, and whether you're of the opinion that autism has always been with us, or autism is a relatively new 'condition'; whether autism is primarily explained by genetics or whether non-genetic environmental factors play a significant role; whether you view autism as a serious public health issue or are more inclined towards the idea of an 'autistic identity'. I'm sure there are other polar opinions to add, but the end result is that [peer-reviewed] data can sometimes become a secondary consideration when it comes to such views and opinions.

Personally, I go with the data. I go with the data that suggest that autism prevalence is still increasing, and not just in the United States (see here and see here for examples). I go with the associated idea that explanations such as 'increasing awareness' and 'diagnostic substitution' probably play some role in the increase, but don't provide a wholly intellectually satisfying explanation for the increasing numbers (see here and see here). I go with the idea that alongside increasing numbers of cases of autism being diagnosed, so more needs to be done in terms of the provision of educational and social support being offered for an often complicated clinical pictures (see here). I also go with the idea that research questions need to be asked (and answered) about what factors could be driving the remarkable increase in autism over the past couple of decades without fear or favour.

I also go with the idea that there needs to be a bit more urgency in the response to such figures. I'm not talking about the use of 'inflammatory' language or soundbites which are bound to make some people nervous or angry. Merely that behind the CDC statistics there are real children and there are families and other loved ones. And they deserve a lot more and a lot better than society is currently providing (see here)...

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[1] Kuehn B. Uptick in Autism. JAMA. 2018 Jun 12;319(22):2264.

[2] Baio J. et al. Prevalence of Autism Spectrum Disorder Among Children Aged 8 Years — Autism and Developmental Disabilities Monitoring Network, 11 Sites, United States, 2014. Morbidity and Mortality Weekly Report (MMWR). 2018; 67(6): 1-23.

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The yet newer CDC estimated autism prevalence rate: 1 in 59 8-years olds with autism in 2014

The report detailing the latest autism prevalence estimates from the US CDC has at last been published [1] coinciding with some other information on the findings. These figures were expected, given the two years that have flown past since the last report put the estimated figure at a stabilised 1 in 68 8-year olds being diagnosed with an autism spectrum disorder (ASD) in 2012 (see here) similar to the report before that which covered the year 2010 (see here).

The latest estimate by Jon Baio and colleagues covering the period 2014 is: 1 in 59 otherwise recorded as 16.8 per 1,000 (1.7%) 8-year-olds diagnosed with an autism spectrum disorder (ASD). Media reporting of the latest figures focuses on the headline finding of that increase in the estimated rate (see here) alongside the 'we don't know why' sentiments voiced by some important authority figures (see here).

So, what other details do the statistics hold and what do they mean?

Well, first and foremost the 'stabilising' of figures noted two years ago at 1 in 68 did not seemingly tell the whole story. I know quite a few people made the most of those non-changing estimates to say that 'autism awareness' and 'changes to diagnostic criteria' and 'diagnostic substitution' were the drivers of the increase and the stabilisation was solely reflective of those factors taking their course. Well, I guess not. Indeed, the restarting of the upward trend kinda suggests that there's probably a lot more going on. It also adds to increasing evidence of a possible 'real' increase in autism (see here). But stand by for the 'it can't be a real increase' sentiments to fly in thick and fast...

Second, as mentioned in the last report from the CDC, we are now presented with not one, but two diagnostic systems to characterise autism or ASD, as the DSM-5 enters service. DSM-5, if you'll remember, is the new classification system that is slowly starting to replace the older DSM-IV criteria. It's also the schedule that *seemed* to be a little more 'selective' in who did and did not qualify for a diagnosis of autism according to other external findings (see here). Did it exert an effect on the most recent autism prevalence estimates? Well, yes it did, as authors noted that: "ASD prevalence was approximately 4% higher based on the historical DSM-IV-TR case definition compared with the new DSM-5 case definition." Although the overall effect was probably not a great one, the more selective case definition provided by DSM-5 in the direction of potentially reducing numbers, contrasts with the upward trend reported. It should also be noted that authors mention how there was "approximately 86% overlap between the two case definitions." But... no mention of the other categorisation called Social Communication Disorder (SCD) (see here) was however included in the latest figures.

Other details are also mentioned in the new report that are worthwhile noting. Almost a third of the children with autism identified in the latest data, who had intellectual functioning data available, were reported to present with an intellectual or learning disability. This tallies with quite a lot of other independent data on the overlap of learning disability with autism. The 4:1 male:female ratio of autism also seemed to hold true in the latest figures. Also: "While a higher percentage of white children were identified with autism compared to black children, and even more so compared to Hispanic children, these disparities were smaller when compared with estimates from previous years." Autism practice it seems, is starting to reach some traditionally under-served populations, that probably contributed in part to the increased estimate noted. I stress the words 'in part' in that last sentence, just in case more sweeping generalisations are put out there to explain away any 'real' increase in the estimated numbers just to better detection of autism in non-white groups.

So, there you have it. An approximate 15% increase in autism estimates in 8-year olds compared with previous figures. As one news report put it: "a 150% increase since 2000." The authors of this most recent CDC report conclude by saying: "ASD is an urgent public health concern that could benefit from enhanced strategies to help identify ASD earlier; to determine possible risk factors; and to address the growing behavioral, educational, residential and occupational needs of this population." I really can't disagree with any of those sentiments.

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[1] Baio J. et al. Prevalence of Autism Spectrum Disorder Among Children Aged 8 Years — Autism and Developmental Disabilities Monitoring Network, 11 Sites, United States, 2014. Morbidity and Mortality Weekly Report (MMWR). 2018; 67(6): 1-23.

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Estimated autism prevalence in Canada in 2015: 1 in 66

"On March 29, 2018, the Public Health Agency of Canada published the first comprehensive review of the prevalence of autism spectrum disorder (ASD) in Canada."

So began the 'what did we find' summary (see here) covering the "Made in Canada" findings detailed in the Canadian National Autism Spectrum Disorder Surveillance System (NASS) 2018 Report (see here) [1]. Pertinent to the year 2015 and including some 88% of the children and young adults living in various participating Provinces and Territory, data was gathered from various sources (education, social services, health) onward to the estimated prevalence of diagnosed autism in Canada.

Their results: "Among children and youth 5–17 years old across seven provinces and territory, the combined prevalence of ASD for the year 2015 is 1 in 66 (15.2 per 1,000)" (bold text added by me).

Details, details, details... Such an estimate applies to children and young adults (youth) diagnosed with autism and does not say anything about the number of adults diagnosed with autism. It only covers those diagnosed with autism based on strict criteria: "The diagnosis of ASD is provided or confirmed by a licensed health care professional(s)... [and] The diagnosis of ASD is based on the clinical criteria in the Diagnostic and Statistical Manual (DSM) for Mental Disorders or the case is identified as ASD in the International Classification for Diseases (ICD)." It does not provide any information on how many people *might* be autistic but not yet in receipt of a diagnosis. Males made up the lion's share of those diagnosed. Most had been diagnosed by the age of 8 years (72%). Oh, and not every Province or Territory showed the same estimated prevalence rate for various potential reasons. And rest.

Also pretty important to the reported findings is the comparison with earlier years estimates: for 3 geographic locations in Canada we see the characteristic 'upward trend' in the estimated prevalence of ASD noted in other sample data from other countries, from around 4-6 per 1,000 in 2003 to between 16-20 per 1,000 in 2015. And when compared with a neighbour to the South (USA) and their estimated autism prevalence stats covering 2012 (see here) coming up with a figure of 1 in 68, the Canadian estimates are not a million miles away,. This, bearing in mind, some differences in the way the different country figures were arrived at and also the time periods covered. That also reminds me, we should be seeing the latest US stats on estimated autism prevalence from the CDC at some point in the (very) near future, and the promise that "the ADDM Network will be able to estimate ASD case status on the basis of both DSM-5 and DSM-IV-TR." Those comparisons should be rather interesting in light of other preliminary data (see here).

What else it there to say? Diagnosed autism is fairly prevalent across Canada (who have some important history in relation to the autism 'numbers game') and I assume we'll be seeing more on their tracking of the diagnosis in future times. Preparation is an important part of the figures being discussed; preparation of education, social and health services to support the numbers of children and young adults being diagnosed now and who, I assume, will eventually be transitioning to adult services. And on the topic of adult services, I'll refer you to Harold Doherty's blog and some of his opinions on adult services in a Canadian setting (see here).

Finally, is the question of 'why' the increase? Well, let's wait and see what those US CDC figures say first and how useful they might be to answering 'why' in the Canadian and other contexts too. I say this accepting that those 'better awareness', 'diagnostic switching' and 'broader criteria' arguments that have long been trumpeted as 'fact' are probably not all there is to see in this area (see here and see here).

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[1] Autism Spectrum Disorder among children and youth in Canada 2018. Public Health Agency of Canada. 2018. March 2018.

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The even newer CDC autism prevalence rate

"For 2012, the combined estimated prevalence of ASD [autism spectrum disorder] among the 11 ADDM [Autism and Developmental Disabilities Monitoring] Network sites was 14.6 per 1,000 (one in 68) children aged 8 years."

So said the report by Deborah Christensen and colleagues [1] continuing a research theme as the CDC map the estimated prevalence of autism in the United States over the years (see here and see here). This time around, as last time covering 2010, the figure settled on is an estimated 1 in 68 8-year olds; although boys were more readily diagnosed than girls (23.6 per 1000 vs. 5.3 per 1000 respectively, translating at 1 in 42 boys and 1 in 189 girls).

Eleven (states) sites brought data to bear in this study, and once again, New Jersey (NJ) came out top in terms of the prevalence estimates (1 in 41). The authors note that "both education and health care records were reviewed" in NJ whereas the site with the lowest prevalence rate, Maryland, only health care records were reviewed. It's also worthwhile noting that although the overall estimated figure for autism prevalence was the same as for the 2012 data, there were some interesting trends according to different sites. So: "Significantly increased ASD prevalence estimates were observed in New Jersey (12%) and Wisconsin (16%). In Missouri, estimated ASD prevalence decreased significantly, by 19%, and at the remaining five sites (Arizona, Colorado, Georgia, North Carolina, and Utah), ASD prevalence estimates did not change."

As per the press release accompanying the data, there were some significant disparities in terms of racial and ethnic groupings. "Estimated ASD prevalence was significantly higher among non-Hispanic white children aged 8 years (15.5 per 1,000) compared with non-Hispanic black children (13.2 per 1,000), and Hispanic (10.1 per 1,000) children aged 8 years." The authors speculate that this is probably less to do with Hispanic and non-Hispanic black racial groupings as being somehow protective of autism and more to do with various barriers to screening and assessment - "Targeted strategies are needed to increase awareness and identification of ASD in minority communities."

There is also the promise of some interesting times ahead for the CDC autism prevalence initiative. The authors make mention of the introduction of the new DSM-5 guidelines (see here) and a suggestion that: "Beginning with the 2014 surveillance year, the ADDM Network will be able to estimate ASD case status on the basis of both DSM-5 and DSM-IV-TR." That'll make for important reading no doubt given the history of DSM and autism (see here).

I'd encourage readers to have a good look at the Christensen paper and draw their own conclusions about the positives and negatives of the approach undertaken and data reported. I do think it is a little too early to talk about a 'plateau' in the autism rates given what we know about the variability of autism across different geographies (see here) and other issues (see here). The authors say as much: "Although the overall prevalence estimate is unchanged from surveillance year 2010, prevalence ranged widely across the ADDM Network and prevalence increases were reported at two sites, suggesting that it is premature to conclude that the rising prevalence of ASD observed during the first decade of the 21st century might be slowing."

Indeed irrespective of the similarity in figures for 2010 and 2012, an estimated 1 in 68 8-year old children with autism still represents a significant number of children.

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[1] Christensen DL. et al. Prevalence and Characteristics of Autism Spectrum Disorder Among Children Aged 8 Years — Autism and Developmental Disabilities Monitoring Network, 11 Sites, United States, 2012. Morbidity and Mortality Weekly Report (MMWR). 2016; 65: 1-23.

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Christensen, D., Baio, J., Braun, K., Bilder, D., Charles, J., Constantino, J., Daniels, J., Durkin, M., Fitzgerald, R., Kurzius-Spencer, M., Lee, L., Pettygrove, S., Robinson, C., Schulz, E., Wells, C., Wingate, M., Zahorodny, W., & Yeargin-Allsopp, M. (2016). Prevalence and Characteristics of Autism Spectrum Disorder Among Children Aged 8 Years — Autism and Developmental Disabilities Monitoring Network, 11 Sites, United States, 2012 MMWR. Surveillance Summaries, 65 (3), 1-23 DOI: 10.15585/mmwr.ss6503a1

The new CDC autism prevalence rate

Whilst quite a lot of media space is currently being devoted to talking about the study by Rich Stoner and colleagues [1] and sweeping generalisations like the BBC headline: Autism 'begins long before birth' with seemingly only little appreciation of the small-scale nature of the study and little details linked to samples being post-mortem tissues, other important autism-related news is also out there.

CDC US autism prevalence estimates @ Autism Speaks 

I'm talking about the latest autism prevalence estimates from the US CDC (Centers for Disease Control and Prevention) for 2010.

The latest report [2] reveals that the overall estimated prevalence for 8-year olds in the United States having an autism spectrum disorder (ASD) in 2010 is:

1 in 68.

Back in 2012 (has it been that long?) I talked about the publication of the estimates based on the 2008 surveillance data which highlighted an estimated 1 in 88 children presenting with an autism spectrum condition [3]. That the latest figures further revise upwards the prevalence estimates follows a trend over quite a few years now as per the graph included in this post taken from the Autism Speaks coverage of this news. The intervening years have seen other reports talking about increased prevalence estimates for autism as per reports here and here and here both in the US and other parts of the world, taking into account factors such as ethnicity too. In light of these estimates, some of which talked about 1 in 48 children with autism I don't think anyone should be too surprised by the latest CDC estimate.

As per my 2012 post on the 1 in 88 figure, I'm sure that the latest CDC estimates will generate further discussions about the hows and whys of the increasing numbers of children being diagnosed with an ASD. I'm willing to take on board arguments about better awareness and improved diagnostic vigilance as accounting for some of the change, but those factors only go so far. Yet again, I'm going to link to the Nature piece from Karen Weintraub [4] on the autism prevalence puzzle and how blanket commentary like 'we're just better at diagnosing autism' is starting to wear a little thin particularly in light of the continued reliance on DSM-IV criteria in this latest estimate.

Perhaps now is the time to start further widening the research agenda when it comes to the question of what is driving the increase in cases of autism to include a few additional points: (a) that autism is probably a plural condition, so 'autisms' over autism which is exquisitely exemplified by the recent BCKDK research, (b) genes and genetic influences are [variably] important to the autisms (see previous point), and (c) genes represent our blueprint but are not necessarily our destiny as per the rise and rise of the science of epigenetics combined with the notion that we don't walk around with all our genes permanently fixed to the 'on' position all the time. That final point in particular opens the door to environment - some facets of environment - also variably impacting on genes, the function of genes, and indeed autism and autism risk. And as we've seen in recent times, how perhaps we should be devoting a little more effort to looking at certain external factors [plural and cumulatively] as potentially playing some [variable] role in the increasing numbers of children being diagnosed with an ASD.

Just sayin'.

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[1] Stoner R. et al. Patches of Disorganization in the Neocortex of Children with Autism. NEJM. 2014; 370: 1209-1219.

[2] Autism and Developmental Disabilities Monitoring Network Surveillance Year 2010 Principal Investigators; Centers for Disease Control and Prevention. Prevalence of autism spectrum disorders--Autism and Developmental Disabilities Monitoring Network, 14 sites, United States, 2010. MMWR Surveill Summ. 2014 Mar 30;63. SS-2.

[3] Autism and Developmental Disabilities Monitoring Network Surveillance Year 2008 Principal Investigators; Centers for Disease Control and Prevention. Prevalence of autism spectrum disorders--Autism and Developmental Disabilities Monitoring Network, 14 sites, United States, 2008. MMWR Surveill Summ. 2012 Mar 30;61(3):1-19.

[4] Weintraub K. The prevalence puzzle: Autism counts. Nature. 2011; 479: 22-24.

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Autism and Developmental Disabilities Monitoring Network Surveillance Year 2010 Principal Investigators (2014). Prevalence of Autism Spectrum Disorder Among Children Aged 8 Years — Autism and Developmental Disabilities Monitoring Network, 11 Sites, United States, 2010 Morbidity & Mortality Weekly Report, 63

CDC and the autism numbers game

Static @ Paul Whiteley

The waiting is over. The speculating is done. They're here...

Three years after the last update in 2009*, the US Centers for Disease Control and Prevention (CDC) have revealed their latest estimate for US childhood autism prevalence.

The 2009 estimate, based on surveillance in 2006, suggested that 1 in 110 US children (roughly equating to 1%) aged 8 years old - so born in 1998 - has an autism spectrum disorder. The caveat to that data was that the estimates fluctuated to some degree across the 11 States included in the analysis ranging from 12.1 per 1000 in the States of Arizona and Missouri to 4.2 per 1000 in the sunshine State of Florida. The overall figures nevertheless represented a 57% increase in the numbers of diagnosed cases compared with data from 2002** which previously estimated a rate of about 1 in 150 US children.

The paper trail of recent autism prevalence studies by the CDC using the same DSM-IV - DSM-IV TR criteria makes for some nice standardised methods for screening and case ascertainment which are not to be sniffed at.

So what is the latest estimate?

1 in 88.
[Update: the full report can be found here***]


Childhood autism in the United States has officially broken through the 1% prevalence threshold.

Are these latest figures a great surprise? Probably not to anyone who has followed the numbers over the years. Some people will remember the South Korea (SK) study from last year (2011) which suggested that 1 in 38 children (2.64% cumulative) may present with an autism spectrum condition. The data from Utah, USA, however, and their suggestion of 1 in 77 children with autism, seemed not to have received the same level of media interest despite being closer to the recent CDC mark. Utah also having the benefit of a good history on estimating autism prevalence down the years.

So, where next?

Based on the new estimate, I assume a familiar story will be put out to account for the change (better awareness, diagnostic substitution, more willingness to diagnose, widening of diagnostic criteria, etc) which whilst perfectly acceptable explanations still might not provide the full picture; not at least according to the Nature article from last year (2011). I have to say that I am always struck by how sure some people are that they know what is driving the increase in cases of autism as per one of the commentators on this recent newspaper article on autism going up here in the UK.

Autism on the rise as a consequence of better awareness? Well we do have World Autism Awareness Day on April 2nd and every year it seems to get bigger and bigger in terms of events and participation. Personally I'd like to think that the over the years of the DSM-IV and ICD-10, most professionals, whether teachers, health visitors, psychologists / psychiatrists, SALTs, know what to look for when it comes to autism in the early years. I think also that we should perhaps not underestimate parents and their observations in the early days of autism manifesting itself as important to this process. I could perhaps argue therefore that the awareness issue is probably to some extent covered in terms of the expertise and the various screening programmes in operation around the globe for autism. I'm not saying that awareness might not be contributory to the increasing prevalence but find it very difficult to say this is the sole 'cause' of the increase.

Diagnostic substitution? Widening of the criteria? Again, possible reasons, although probably more important reasons about 10-15 years ago following the replacement of DSM-III for example. Nowadays I'm not as sure that they still carry the same sort of weight.

So what are we left with? I've talked quite a bit on this blog about the rise and rise of epigenetics with autism in mind; that is genes and environment interacting together. Environment covers a lot of ground and I don't really want to start speculating on what facets of environment may or may not be linked. I do however think that we need to start shifting research attention away from the purely 'autism is genetic' model which has persisted for quite a few years. Autism may well have genetic underpinnings, which variably act on different people to different extents, but I don't seriously think that anyone would entertain all autism as being solely genetic. Indeed, epigenetics is beginning to turn quite a few areas on their research head and, in coming years, I am sure we will hear much more about it.

One final point to make: if the changes being suggested to DSM-5 (and I assume ICD-11 for that matter) for autism are actually implemented, we could be looking at a totally new way of coding for autism in subsequent CDC and other reports which will break those years of standardised measure based on DSM-IV. Will these changes affect the numbers of cases, and if so, in what direction? Mmm, a tough one.

* Prevalence of autism spectrum disorders - Autism and Developmental Disabilities Monitoring Network, United States, 2006. Autism and Developmental Disabilities Monitoring Network
MMWR Surveill Summ. 2009; 58: 1-20.

** Prevalence of autism spectrum disorders - Autism and Developmental Disabilities Monitoring Network, 14 sites, United States, 2002. Autism and Developmental Disabilities Monitoring Network
MMWR Surveill Summ. 2009; 58: 1-20.

*** Prevalence of autism spectrum disorders - Autism and Developmental Disabilities Monitoring Network, 14 sites, United States 2008. Autism and Developmental Disabilities Monitoring Network
MMWR Surveill Summ. 2012; 61: 1-19