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Autism

Trying to Predict the Future: Trajectories in Autism

Predicting individual trajectories is critical, but is not currently possible.

"I just didn't know what to say. I felt so badly..." is what Sarah,** one of the PhD students in our autism clinic, said to me yesterday. She was referring to a feedback phone call in which she had told a parent about the results of his child's autism screening. The father had asked about his child's future: are the symptoms we saw something his son would grow out of? Would the symptoms get worse over time?

Essentially, he was asking, "What will the future look like?"

What to say when you don't know

I reassured Sarah that her answer--which was that unfortunately we just do not know enough about trajectories to predict any individual child's future--was exactly right. But I knew my reassurance did little to ease her guilt. I know how she feels because I still feel the same way when parents ask me those questions--even when I know the "right" and honest answer is what Sarah said--that we are unable to predict what any individual child's future will look like.

After my conversation with Sarah, I decided to look into some expert opinions about trajectories, and what we know (and do not know) about autism symptom severity over time.

What does the research say?

A 2015 longitudinal study of 421 preschool aged children with ASD sheds some light on trajectories of symptom severity. The authors found that there were 2 separate trajectories that best explained how children's symptoms of autism changed over time. One group (Group 1; about 11% of the total sample) had less severe symptoms at the time of diagnosis, and showed symptom improvement over time. A second group (Group 2; about 89% of the total sample) had more severe symptoms at the time of diagnosis and a stable trajectory over time. Differences between the two groups went beyond autism symptom severity. At age 6, the two groups differed significantly on measures of language, developmental index, and behaviors associated with anxiety and depression. Essentially, this means that Group 1 (the less severe symptoms and improving group), had better language scores, higher developmental scores, and less symptoms associated with anxiety and depression at age 6 compared to Group 2 (the more severe symptoms and stable group).

Expert Opinions

I also found a great opinion piece on the autism news website spectrum. The author, Stelios Georgiades, noted that individual trajectories are not well understood in autism, and longitudinal research projects need to explore not only what the trajectories are on a group level (like in the above study), but also why some children start on one and then seemingly move to another over time. The opinion piece linked to a 2017 article by Georgiades and two colleagues that introduces the concept of "chronogeneity." Chronogeneity refers to the study of heterogeneity in autism in relation to time, e.g. studying group and individual trajectories over time, as well as how given individuals might deviate from group trajectories across time.

This concept is an important one, especially because most clinicians know children who didn't follow expected trajectories, but none of us quite know why. For example, I have seen minimally verbal 3-year-olds with high levels of autism severity go on to develop more language skills than I would have predicted. However, I've also seen and heard about the opposite: highly verbal young children with relatively low levels of autism severity who go on to have significant challenges with peer relationships and develop anxiety and/or depression.

The above examples highlight the impossibility of predicting the future for children with ASD. In general, we know that more severely affected children are more likely to remain severely affected than those who initially present with less severe symptoms. But the beginning of that sentence, "in general", is exactly the problem. We know those things from group research studies, but not at the individual level, so we cannot say to a given parent what their child's future will look like with any degree of certainty. We do not yet have a good understanding of why two children of equal symptom severity at age 3 might have wildly different outcomes at age 10, or why two children who both enroll in the same evidence based early intervention program might not demonstrate the same improvements over time.

Takeaways

There is good reason for the often used phrase, "If you've met one person with autism, you've met one person with autism" (I found out that this famous quote is from Dr. Stephen Shore--link to an interesting Q&A with him here). The phrase has stuck with me since I first heard it as an undergraduate, and continues to stick with me as a professor. There is no "one size fits all" in autism. Just as the condition itself is a spectrum, so are the outcomes and lifelong trajectories.

Unfortunately, that means we are not in a place to answer parents when they ask us, "What does my son's or daughter's future look like?" We can tell them what the research says (with the dreaded, "in general" caveat), but largely need to be up-front and tell them that there is no good way of predicting future outcomes.

Sometimes the right answer is not particularly informative, and it is our job to offer support and understanding, and to empathize with their frustration in the face of uncertainty. As clinicians and scientists, that is the best we can do for now.

**Name changed for privacy.

References

Szatmari P, Georgiades S, Duku E, et al. Developmental Trajectories of Symptom Severity and Adaptive Functioning in an Inception Cohort of Preschool Children With Autism Spectrum Disorder. JAMA Psychiatry.2015;72(3):276–283. doi:10.1001/jamapsychiatry.2014.2463

Georgiades, S. , Bishop, S. L. and Frazier, T. (2017), Editorial Perspective: Longitudinal research in autism – introducing the concept of ‘chronogeneity’. J Child Psychol Psychiatr, 58: 634-636. doi:10.1111/jcpp.12690

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More from Katherine K.M. Stavropoulos Ph.D.
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