Gustational sensitivity and autism: a matter of taste

A sensory friend @ Paul Whiteley

Given the all-but accepted revisions for diagnosing autism spectrum conditions in DSM-5, there is one area of change to the Diagnostic & Statistical Manual entry that I think most people would be satisfied with: the overt inclusion of criteria surrounding unusual reactivity/interest to sensory input or sensory aspects of the environment.

Indeed whilst such sensory - perceptual issues in cases of autism have been known about for some years, many people (including me) have probably wondered to themselves why has it taken so long for this important factor for many people with autism to be included as part of the way the condition is assessed and diagnosed. Well now it is.. or at least will be fairly soon, minus any last minute changes that is.

Having said all that, just because such sensory issues are to be included in the diagnostic text, doesn't mean there is necessarily any consensus on what can be done about them as and when required, as per the recent policy statement by the American Academy of Pediatrics* (full-text).

I digress.

You could literally write a whole book about sensory issues in relation to autism - indeed some people have - but for this post, I'm zooming in on one part of that sensory issue dealing with taste or to use the proper scientific term, gustational sensitivity. I'm also sticking with the term 'sensitivity' in this post as per the assumption that some people on the autism spectrum seem to be particularly sensitive - hypersensitive - to certain types of taste and acknowledging also the opposing result, hyposensitivity to be also potentially present. I hasten to add that everyone, whether autistic or not, has their own individual tastes, likes and dislikes; taste is a very personal thing as per the various discussions on phenylthiocarbamide (PTC) perception which some may remember with regards to 'diagnosing' schizophrenia.

I remember about 15 years ago seeing gustational sensitivity in action with a child with autism. It was during a visit to see a child involved in one of our early research studies to talk to the parents about the food and feeding patterns they were seeing. The child was thirsty and mum brought a drink of cordial for the child. The drink seemed pretty concentrated and when asked about this, mum replied something along the lines of "XX always likes lots of cordial". Indeed not being a connoisseur of cordial drinks, even I could see that there was more cordial than water. That drink would probably have been pretty strong. Such observations have been accompanied by other anecdotal reports of preferences for strong tasting foods in cases of autism. I hasten to add however that not everyone with autism can be found tucking into a vindaloo curry at every opportunity for example, as per this abstract from IMFAR 2012.

Research into the gustational aspects to some cases of autism is still quite thin on the ground. It all really kicked off in the early noughties with this study** by quite a familiar name, Sally Rogers (and colleagues) who noted some interesting differences in parent reported sensory symptoms in children with autism. Taste and smell seemed to show the greatest difference in autism compared with cases of developmental delay, Fragile X syndrome and asymptomatic controls. Sample sizes were relatively small but the results were interesting.

Sue Leekam and colleagues*** (previously from Durham University just down the road from me) were among other groups to further categorise sensory issues in cases of autism; again, with specific reference to smell and taste. This paper by Bennetto and colleagues**** (full-text) put some 'meat on to the bones' with their characterisation of taste (sweet, salty, sour & bitter) perception in autism. I note also reference to a bit of a blast from the past with the use of 'Sniffin' sticks'.

A couple of more papers to mention then I'm finished. This paper by Lane and colleagues***** (including another familiar name, Manya Angley) looked at the possibility of subtyping children with autism on the basis of sensory processing including category headers like taste and smell. And finally, Tavassoli and Baron-Cohen****** add to the evidence base on issues with taste in adults with autism.

From this and other evidence, both scientific and from lay sources, it is fairly clear that at least some people on the autism spectrum seem to present with issues related to the sensory aspects of taste. I've not really talked about related issues such as smell, texture (food texture) and issues like pica which seem also to be related to gustation but nevertheless one needs to bear these in mind also.

The mechanism is still unclear as to why taste perception might be attenuated for some people, accepting that personal preference should not be excluded from any explanation and the realisation of some degree of inter-relatedness between the various senses we all use. I could speculate on one possible mechanism of effect although with the caveat that lots of processes will most likely be (variably) involved, including some recent suggestion of more physiological issues potentially present as per the article from Betalli and colleagues****** (which probably deserves a blog post on its own).

To finish, taste can mean more than one thing; and to show that I have very little of it when it comes to fashions and trends, and in honour of this years Eurovision... whatever it was, nul points for Jemini back in 2003. (Bravo to the Hump for not coming last).

P.S. The hedgehog picture was taken a few nights back outside my house as the little critter was foraging for some tasty earthworms in the garden.

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* Sensory Integration Therapies for Children With Developmental and Behavioral Disorders.
Section on complementary and integrative medicine; Council on children with disabilities.
Pediatrics. May 2012

** Rogers SJ. et al. Parent reports of sensory symptoms in toddlers with autism and those with other developmental disorders. JADD. 2003; 33: 631-642.

*** Leekam SR. et al. Describing the sensory abnormalities of children and adults with autism. JADD. 2007; 37: 894-910.

**** Bennetto L. et al. Olfaction and taste processing in autism. Biological Psychiatry. 2007; 62: 1015-1021.

***** Lane AE. et al. Sensory processing subtypes in autism: association with adaptive behavior. JADD. 2010; 40: 112-122.

****** Tavassoli T. & Baron-Cohen S. Taste identification in adults with autism spectrum conditions. JADD.  October 2011.

******* Betalli P. et al. Autism and esophageal achalasia in childhood: a possible correlation? Report on three cases. Diseases of the Esophagus. May 2012
DOI: 10.1111/j.1442-2050.2012.01358.x

The nose knows

I always consider it a bit of bonus when PubMed lists a paper which is a bit out of left-field. Not that I am complaining when more "mainstream" science is also published. But every now and again something crops up leading to one of those 'mmm?' moments. The paper in question this time relates to the curious title of this post (which incidentally was a book I remember reading as a child, one of the few, I might add, myself not being a great reader of books in general): odor detection threshold, but not odor identification, is impaired in children with autism.

Why was I so drawn to this paper? Well, I can't say for sure. Maybe it was the connection to perception and the human senses, some of which I have blogged about previously in relation to autism (vision and hearing). Maybe it was the use of the unusual 'Sniffin Sticks' test. Maybe it was the focus on one of the more under-represented senses. I can't say.

The study and findings: a small-ish sized group with Asperger syndrome/high-functioning autism compared with age and gender matched non-AS controls.  The odor/odour detection threshold (the point at which a smell is smelled) using the Sniffin' Sticks method was different (higher) in the AS compared to control groups. The AS group were also better at smelling orange but worse at smelling cloves (no other significant differences in other smells were found). The same group have published in this area before and the other research in this area is equivocal.

Assuming that there is a biological explanation for the results, I do wonder if this might be a small part of the proposed social side of things relevant to autism. More and more the research seems to imply that the traditionally held beliefs on problems with social cues in autism for example are not being borne out by the research. Even eye movements in relation to attention in autism appear fairly typical.

Smell on the other hand is our hidden social moderator. Aside from providing us with quite a bit of information about the person or place or other thing we are presented with, smell is also tied into things like pheromones. I know that there is still some debate on 'the human sex scent' and whether we are so swayed by it. One however only needs to look at menstrual synchrony to see that there may still be something in it, even at a subconscious level.

One could also assume that issues with smell might also tie into problems with feeding behaviours given that the olfactory and gustational (taste) senses are inter-linked (as we all find out when we eat whilst having a cold). I do perhaps think it might be a step too far to say that the feeding problems described in autism are exclusively tied into a problem with smell, but you never know, it might be at least contributory.

I would be interested to see what other research comes out in this area in future.