The trajectories autistic children can follow: A guide to the research

By Stephen Gentles

One of the hoped-for uses of trajectory research in children with autism is to provide answers to questions that a parent or caregiver might ask a clinician about their autistic child: “What will they be like as they get older?” You can imagine how important something like language development might be. But trajectory research has provided important knowledge about autistic child development for many other different outcomes.

The full range of this research has never been thoroughly mapped out until now. Like the index in a book, our recent open-access scoping review of trajectory research in autistic children provides a comprehensive resource guide that shows different consumers of such research—such as caregivers, clinicians, and researchers planning their next trajectory study—where to find the trajectory study reports they might be interested in.

Trajectory studies involve measuring developmental or health-related outcomes at three or more timepoints, as opposed to measuring them at two timepoints like a typical cohort study does. More timepoints allows you to characterize the shape, or changes in the rate of change of something over time. These have been described as turning points, which you can think of as an elbow in the slope of something that changes over time. From a caregiver’s perspective this might be noticed as accelerations, plateaus, or slowdowns in a child’s development.

For this review, we set out to identify and summarize the published breadth of research that uses a trajectory study design to look at development in children (to age 18 years) diagnosed with autism. We followed the various scoping review guidance that has been published over the years (e.g., 2005, 2010, 2016, and 2020), adhered to reporting standards for scoping reviews, and published the review’s protocol open access.

In contrast to classic systematic reviews, where the aim is to summarize the findings of research on a more specific research question, scoping reviews are not considered an appropriate method for summarizing findings. Rather we summarized other characteristics of the available research such as the many outcomes studied, and key aspects of the methods used for these studies.

Altogether, 103 studies were included and summarized. One of the most noticeable products of this paper is the series of 10 figures that summarize the research available on each of the top ten most-studied outcome domains. These figures provide resources that not only show the specific studies available in each outcome, but also the ages covered, the measures used, and other aspects. Importantly, they highlight gaps not studied. For example, only two studies of autism symptom severity had any timepoints beyond age 12.

Something that can make trajectory study reports challenging for some readers is the multitude of statistical methods used to generate the results. To help make sense of the 35 terms used to describe the many different statistical methods researchers reported using, we included a table categorizing each method into three overall approaches used in trajectory research. These three approaches are in turn described in accessible language. This summary of statistical approaches, methods and terms can improve understanding for novice readers and researchers alike, and provides an authoritative list of search terms that can be used in future reviews.

The review also featured a limited but meaningful level of community involvement. We invited, and compensated, one autistic adult and one caregiver to provide their interpretations of the results, and this was worked into the discussion as a concretely useful commentary on the relevance of specific outcomes for future trajectory research.

This scoping review will be useful for several audiences, including trajectory researchers planning their next study, systematic reviewers who want to know if there is enough research to pool results on a specific outcome domain, and autistic people and caregivers of autistic children who are known to be big consumers of primary research. Anyone wanting to know where to find the research about the shapes of development in autistic children will find this review a valuable resource.

Article Details
Trajectory research in children with an autism diagnosis: A scoping review
Stephen J Gentles, Elise C Ng-Cordell, Michelle C Hunsche, Alana J McVey, E Dimitra Bednar, Yun-Ju Chen, Eric Duku, Connor M Kerns, Laura Banfield, Peter Szatmari, Stelios Georgiades
First Published May 16, 2023 Research Article
DOI: 10.1177/13623613231170280
Autism

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