The diagnosis of an autism spectrum condition is predominantly (nay exclusively) based on a subjective judgement of whether clinical behavioural criteria are met, also incorporating an analysis of a person's developmental history.
In other words, parents and caregivers are often vital to the diagnostic process as a function of their recall of their child's early medical and developmental onset history, and events leading towards the presentation of symptoms.
Early diagnosis of autism is the goal; although often, because of the way symptoms present or the finite resources available to access assessment services, there are delays from time of symptom onset / recognition to receipt of a formal diagnosis. In some cases, this delay registers in the years rather than months or weeks.
I say all this because a new paper by Cathy Lord and colleagues discusses an important issue relating to the recall of symptoms, the 'telescoping' effect in caregiver reports - that is, a bias based on the reporting of events. Telescoping can be forward or backwards; so remembering events either closer or more distant than they really are.
Before anyone takes this issue too personally, I must add that we all do it. Ask someone about when a recent event happened and the chances are that they will be slightly outside of the actual time frame - 'when did I last go out for a meal?', 'when did I last call my parents', 'at what age did my children start to walk' - all biased by our failing memory (assuming that there is no other corroborating evidence such as videos or diary entries).
Lord and colleagues suggested some significant telescoping effects when the Autism Diagnostic Interview (ADI) was administered to caregivers over various occasions of their child's early years (2,3,5,9 years of age), specifically in the area of language milestones (acquisition of language, use of phrase speech, etc). Importantly however, when it came to the age of first concern over symptoms, caregivers seemed to be pretty consistent.
What does this all mean?
Well when it comes to dating when symptoms started, current psychological theory would perhaps suggest that this date is an anchor point for parents / caregivers. Whether due to a realisation that symptoms present and the subsequent emotional effects of this (emotions and memory seem to be strongly connected) or the associated interactions with other people (teachers, health visitors, physicians) as a result, age of first concern seems to stick in the memory.
Dating the various features of language acquisition proved more difficult. I assume much of this is because many things related to language are not tied into just one date. Remember the scene in Meet the Fockers when the little boy utters his first words (I won't repeat them here!). Unless a child says such an extreme word, chances are most people won't be able to date accurately when their child's first word happened just from memory. Likewise can anyone name the date when their child went from using single words to phrase speech? With all the will in the world, most people will be inaccurate because again our memory needs some kind of anchor and such a transition process is often not tied into one date.
One final thing related to this paper: at the end of the abstract, the authors say: "Results support proposals to remove specific age-based criteria in the diagnosis of ASD". For those who read my post on the new proposals for the DSM-V entry for autism, and in particular the proposed changes to a 'dyad of impairments', this sounds to me like the DSM-V proposal is shortly going to become a reality.
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