Is autism contagious?

by Benison O'Reilly on Friday, May 14th, 2010

In the introduction to the Australian Autism Handbook I write that having Joe has made me ‘a kinder and wiser person’, one who no longer ’sweats on the small stuff’.  Two years later I can confirm that still rings true.  I remain more tolerant of life’s vicissitudes and my fellow human beings and their failings. Not much upsets me.

However, there is one aspect of life where I remain less tolerant and that concerns my children.  If anyone seriously slights one of my boys I feel it keenly. This particularly applies if anyone slights Joe.

Anyway, without giving too much away, there was once a woman of my acquaintance — a woman with neurotypical children— who made it clear that— despite my gestures of friendship— she wanted as little to do with Joe and me as possible.  Was it me? Or was it Joe? I’m not sure. I can rationalise the former, but the latter…not so easily.

I once said to my husband, ‘Perhaps she thinks autism is contagious’.

Thus, I was surprised to find that a recent study suggests that it is.

Okay, I’m bending the truth a bit.  But hopefully I’ve caught your attention.

What the study, by researchers from Columbia University, did find is that children living near a child who has been previously diagnosed with autism have a much higher chance of being diagnosed themselves in the following year.

However, the researchers do not believe this is because autism is contagious. Nor do they think it’s due to an environmental agent.  They believe it is because parents are learning about autism from other parents who have a child on the spectrum; they are being educated about symptoms, and the process of obtaining a diagnosis and treatment, from people who have already been through the process with their own child.

In the study, entitled Social Influence and the Autism Epidemic, researchers looked at data on over 304,000 children born in California between 1997 and 2003. They found that children who live within 250 metres of a child with autism have a 42% higher chance of being diagnosed with an ASD in the following year compared with children who do not live near a child with autism. Children who live between 250 metres and 500 metres from a child with autism were 22% more likely to be diagnosed. As we would predict, the study showed the proximity effect to be strongest amongst children with high functioning autism, the sort of kids whose symptoms and behaviours might have been explained away as ‘oddness’ in earlier times.

The researchers eliminated competing explanations, such as environmental toxins or viral transmission through a series of statistical tests. They also considered other social factors that could be driving the autism ‘epidemic’, such as maternal age and education standards (some studies have found that older parents are more likely to have a child with an ASD, whilst others suggest that better educated parents are more likely to obtain a diagnosis for their child). Whilst the Columbia University team found that each of these social factors appears to play a role in the rising prevalence of autism, the so-called ‘social influence’ phenomenon exerted the most powerful effect.

The researchers conclude:

One does not “catch” autism from someone else, yet a social diffusion process contributes significantly to the increased prevalence of autism.

Looks like we might have found another piece in intriguing puzzle of why autism diagnoses are on the increase.

The paper, published in the American Journal of Sociology, is available free to download on the link below.

Ka‐Yuet Liu, Marissa King, and Peter S. Bearman. Social influence and the autism epidemic.

American Journal of Sociology 2010 115:5, 1387-1434

http://www.journals.uchicago.edu/doi/full/10.1086/651448

Or read more commentary on the study at Science Daily:

www.sciencedaily.com/releases/2010/04/100408161017.htm

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1 in 110

by Benison O'Reilly on Tuesday, February 16th, 2010

At Christmas time I said I planned to write about the latest CDC (US Centers for Disease Control and Prevention) ASD prevalence data, released on December 18 last year. Finally I’ve got around to doing it.

There were some mutterings on the Internet that we would have confirmation of that 1 in 100 figure, which was reported in a couple of other studies last year, but the CDC prevalence—amongst 8-year olds in 2006—was subsequently revealed to be the slightly less newsworthy  1 in 110. Still, that’s a big increase from the previous survey conducted in 2002.

The full title of the study is: Prevalence of Autism Spectrum Disorders — Autism and Developmental Disabilities Monitoring Network, United States, 2006. MMWR 2009; 58(SS10):1-20

Prevalence was estimated through a retrospective review of records in eleven sites participating in the Autism and Developmental Disabilities Monitoring (ADDM) Network. To analyse changes in ASD prevalence, CDC compared the 2006 data with corresponding 2002 data, collected from 10 sites (all sites the same with the exception of Florida, which was not included in the 2002 survey). Children aged 8 years with a diagnosis of an ASD or descriptions consistent with an ASD were identified through screening and review of health and education records.

Overall 2,757 (0.9%) of 307,790 children aged 8 years were identified as having an ASD, indicating an overall average prevalence of 9.0 per 1,000 population. Thus in 2006, on average, approximately 1% or one child in every 110 was classified as having an ASD.

The average prevalence of ASDs among children aged 8 years increased 57% from 2002 to 2006.  The researchers believe that whilst some of the increases are due to better detection, a true increase in risk cannot be ruled out.

Delays in diagnosis persisted (average age at diagnosis was 54 months) but ASDs were diagnosed by professionals at earlier ages in 2006 than in 2002.  Forty-one percent of children with an ASD also had signs of intellectual disability, confirming what a lot of us already knew: the majority of people on the spectrum are not intellectually impaired, as originally believed.

If you’re interested, more information is available at:

www.cdc.gov/ncbddd/features/counting-autism.html

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1 in 100, Part 2

by Benison O'Reilly on Saturday, October 24th, 2009

A couple of weeks ago I blogged about a recent British study which found an estimated 1 in 100 adults were on the autism spectrum. Today I will follow up with a report on a 2007 American survey of children that reached similar conclusions.  In fact, the US survey, which questioned a random sample of over 78,000 parents of children aged 3-17 years, actually found a prevalence of 110 per 10,000 or 1 in 91 in this age group. However, I’m sticking to my title, and after reading the survey methods and results I’d probably caution against hanging a huge amount of weight on that 1 in 91 figure.

The study, published in a recent issue of the medical journal Pediatrics, was part of 2007 National Survey of Children’s Health. ¹ Parents or guardians were asked if they had ever been told by a doctor or other health care provider that their child had ‘autism, Asperger disorder, pervasive developmental disorder, or other autism spectrum disorder’. If parents answered yes, they were asked if their child currently had autism or ASD and, if so, to provide a qualitative ranking of severity. Children were only classified as having ASD if their parents answered yes to both the first two questions (i.e. the parents claimed their child currently had ASD).

What seems surprising about this survey is that an unexpectedly large number of parents (representing 38.2% of those children who met the ever-reported criterion) answered no to that second question; that is, they claimed their child had previously been diagnosed with an ASD, but did not currently have the condition.  Thirty-eight percent sounds very high. It would be wonderful if we could declare this a success story for early intervention, but the authors propose a few other reasons:  possible misdiagnosis  in very young children (subsequently revised);  that ASD was once suspected at developmental screening but later ruled out and  thus the child was never really ‘diagnosed’;  diagnostic substitution  (where some children with another developmental condition might have at one stage been claimed to have an ASD to access ASD-specific funding/services);  and finally that some parents may have answered ‘no’ to the second question because their child no longer received special education or autism-specific services for the condition.

Researchers also found that the odds for boys having an ASD were 4 times as large as the odds for girls (consistent with previous research) and that non-Hispanic black and non-Hispanic multiracial children had 57% and 42% lower odds, respectively, of having an ASD than non-Hispanic white children (possibly due to poorer access to ASD diagnostic and intervention services).

Because ASD status in this survey based only on parental report and not confirmed by a health care worker, I’d suggest we treat that 1 in 91 figure with a bit of caution (although a quick search on Google suggests few others have thought to). However, whatever the case, the prevalence of ASD in this survey was found to be higher than previously reported and it appears that 1 in 100 (or 1%) figure is looking more and more likely (there is apparently a Center for Disease Control study yet to come).  The authors of the Pediatrics paper suggest that more inclusive survey questions, increased public awareness, and improved screening and identification by health care workers may go some way to explain this finding.

1. Kogan MD, et al. Prevalence of parent-reported diagnosis of autism spectrum disorder among children in the US, 2007. Pediatrics 2009; 124: 0000 [accessed October 6, 2009]

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1 in 100, Part 1

by Benison O'Reilly on Wednesday, October 7th, 2009

Studies published in the last month on both sides of the Atlantic point to an ASD prevalence of around 1 in 100.  Whilst the US research in children (to be discussed in a future blog) has provoked familiar cries of an ‘autism epidemic’, the British research was actually conducted in adults and supports what some researchers have been saying for years:  autism spectrum disorders have always been with us, but our recognition of them has grown immeasurably in recent years.

The official title of the report is: Autism Spectrum Disorders in adults living in households throughout England: Report from the Adult Psychiatric Morbidity Survey 2007 and it’s available for all to read at the NHS Information Centre: www.ic.nhs.uk/

As the title implies, the ASD research was part of a larger study on psychiatric morbidity. A random sample of adults aged 16 years and older was screened for ASD using a 20 item version of the Autism Quotient (AQ-20).  A subset of respondents with medium to high AQ-20 scores was selected to take part in a phase two interview, where assessments were carried out by clinically trained interviewers using the Autism Diagnostic Observation Schedule (ADOS). The results were weighted to generate a prevalence rate for the population as a whole.

Using a recommended threshold score on the ADOS, 1.0% of the adult population was assessed as having an ASD (i.e. Autistic Disorder, PDDNOS or Asperger’s Syndrome). The rate was higher in men (1.8%) than women (0.2%), consistent with childhood population studies.

Other findings included:

People who were single were more likely to be assessed with ASD.

The rate of ASD was lowest among those with a degree level qualification (0.2%) and highest among those with no qualifications (2.1%).

Those living in accommodation rented from a social landlord were the most likely to have ASD.

Being of low predicted verbal IQ was also associated with presence of ASD.

There was no indication of any increased use of treatment or services for mental or emotional problems among people with ASD (the implication being that they were underutilising services, not that they didn’t need them).

Because of the small sample size, the investigators advise caution interpreting the population distribution of ASD (particularly among women) but the results are interesting in that they suggest that rates of autism are broadly consistent across the age groups; that is, it’s as much a disorder of adults as it is of children.

On a personal note, I can’t help wondering how many adults on the spectrum are out there, not feeling all that ‘disabled’ and just quietly getting on with their lives.

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