What they found was even more complex than expected. Instead of finding that some children show low levels of social communication from very early in life. A second group has early high levels of social communication, followed by significant decreases over time (regression). But, there was a third group: a group which was more typical in development followed by not regression, but a plateau in progress in social communication.
The numbers of children in the study are small (53 autistic children), making it unlikely to get a precise idea of what fraction of the children follow each trajectory. According to the IMFAR abstract for this study :
Bayesian Information Criteria were used to select the number of trajectories that best fit the data. There was strong support from coded home video for 3 onset trajectories. The first “early onset” trajectory (n = 20) displayed low rates of social-communication behavior at all ages. The second “regression” trajectory (n = 20) displayed high levels of social-communication behavior early in life and significantly declined over time. The third “plateau” trajectory (n = 12) was similar to the typical children early in life but did not progress as expected. There was no support for a mixed (early signs + regression) trajectory.
Here is the abstract for the published paper:
The onset of autism is usually conceptualized as occurring in one of two patterns, early onset or regressive. This study examined the number and shape of trajectories of symptom onset evident in coded home movies of children with autism and examined their correspondence with parent report of onset.
Four social-communicative behaviors were coded from the home video of children with autism (n = 52) or typical development (n = 23). All home videos from 6 through 24 months of age were coded (3199 segments). Latent class modeling was used to characterize trajectories and determine the optimal number needed to describe the coded home video. These trajectories were then compared with parent reports of onset patterns, as defined by the Autism Diagnostic Interview-Revised.
A three-trajectory model best fit the data from the participants with autism. One trajectory displayed low levels of social-communication across time. A second trajectory displayed high levels of social-communication early in life, followed by a significant decrease over time. A third trajectory displayed initial levels of behavior that were similar to the typically developing group but little progress in social-communication with age. There was poor correspondence between home video-based trajectories and parent report of onset.
More than two onset categories may be needed to describe the ways in which symptoms emerge in children with autism. There is low agreement between parent report and home video, suggesting that methods for improving parent report of early development must be developed.
The last statement in the results is obviously intriguing. “There was poor correspondence between home video-based trajectories and parent report of onset.”
Here is the segment of the IMFAR abstract:
There was poor correspondence between parent report and home video classifications (kappa = .11, p = .30). Only 9 of 20 participants whose home video displayed clear evidence of a major decline in social-communication behavior were reported to have had a regression by parents. Only 8 of 20 participants with evidence of early delays in social-communication on video were reported to demonstrate an early onset pattern by parents. Of the 10 whose parents described a plateau, only 3 had home video consistent with this pattern.
So, none of the three groups were able to correctly recall the trajectory. Not the parents of kids who regressed. Not the parents of kids who plateaued. Not the parents of kids who had early onset autism.
As parents we’d like to see ourselves as the experts of our children. And, frankly, we are. No one else knows them like we do. But that doesn’t make us infallible.
That IS the most important finding in the study - the poor correlation of video evidence with parental memory. But it does beg the question of whether the video clips were typical, and whether the raters' observations can, in fact, be correlated with the far more 'instinctive' and holistic view of parental experience? Observations have a behavioural bias, which can sometimes be superficial. But on the other hand, diagnosis is usually done on the basis of behaviours.
I'm going to have to think some more about this one.....
Sadly, I have talked to a few parents that swear their child regressed around the age of 2 only to find that a lot of signs were really there much earlier.
So yeah, I could definitely understand how stories might not always match up.
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That is not surprising, actually. You don't know what you are looking at with a very young child as a parent - and before you reach an awareness that something is not as expected, you might miss all kinds of signs. As humans we really only see what we are looking for, and have a remarkable capacity to reshape facts to fit a pattern that we expect to find -- in the present or in our memories of the past.
Considering that babies don't even social smile before a certain point, how is a parent to realize that things are not progressing as they should? There are some big steps around 1 year to 16 months that so many kids fail to take, but the cumulative effect of those missed steps is finally apparent around 20 months. The difficulty is in making parents understand that their perception of the situation might not match an objective description for many reasons that have nothing to do with your qualities as a parent.
Hello friends -
The Kennedy Kreiger group has been talking about plateau for a while now.
Plateau (n=17%): Display of only mild developmental delays until the child experiences a gradual to abrupt developmental halt that restricts further advancement of skills
Does this mean that we can finally, finally put an end to the narrative friendly, "autism is not developmental stasis, but developmental delay" canard?