Researchers studying preschool children with autism spectrum disorder found that symptom severity and adaptive functioning varied among the children at diagnosis and changed over time.

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Previous literature has described autism spectrum disorder as a “persisting and stable” impairment. However, a new study suggests there are a number of different developmental trajectories to the condition.

In a new study, Dr. Peter Szatmari and colleagues evaluate the developmental trajectories of these two domains of autism spectrum disorder (ASD). Some differences were observed by the team to increase by the time the children reached the age of 6.

ASD is a condition that is characterized by repetitive behavior and social impairment such as difficulty with communication. The severity of ASD symptoms ranges widely, from mild impairment to severe disability.

Prior to this study, published in JAMA Psychiatry, the association between symptom severity and adaptive functioning over time had not been investigated. According to the researchers, current literature on the subject describes ASD as a lifelong condition involving persisting and stable impairments.

A total of 421 newly diagnosed preschool children with ASD participated in the multisite longitudinal Pathways in ASD Study. The researchers collected data at up to four separate points – from time of diagnosis until the age of 6 – in order to trace the developmental trajectory of each child.

Symptom severity was measured using the Autism Diagnostic Observation Schedule (ADOS) and adaptive function was assessed using the Vineland Adaptive Behavior Scales, Second Edition.

The researchers observed two distinct trajectories for symptom severity among the participants. While the majority of the children (88.6%) had severe symptoms and a stable trajectory, 11.4% of the children were found to have less severe symptoms with a trajectory of improvement.

The sex of the participants was a predictor of which trajectory group the children were in, with female participants more likely to have less severe symptoms with an improving trajectory.

Results also showed three distinct trajectories for adaptive functioning:

  • Low functioning with a worsening trajectory – 29.2%
  • Moderate functioning with a stable trajectory – 49.9%
  • High functioning with an improving trajectory – 20.9%.

A number of variables were associated with the grouping for adaptive functioning. Scores in language and cognitive tests taken at the baseline and age at diagnosis influenced which trajectory group participants belonged to.

“Although there is certainly a link (based on cross-sectional correlations) between a child’s autistic symptom severity and adaptive functioning at any given point, longitudinal data presented herein suggest that this association is much more complex over time,” write the authors.

Only 58.2% of children and families initially approached for the study agreed to participate fully. The authors acknowledge that they cannot be sure that these children are similar to those that successfully participated in the study for its entire duration. Further research is required to assess whether the findings can be generalized.

A limited number of data points also restricts the authors from estimating trajectory curves for the participants over time, although it is hoped that additional assessments currently in progress will address this limitation.

The authors state their findings could have important implications for surveillance and early identification efforts.

“It is imperative that a flexible suite of interventions that target both autistic symptom severity and adaptive functioning should be implemented and tailored to each child’s strengths and difficulties,” the authors conclude.

Recently, Medical News Today reported on a study suggesting that video-based treatment may improve autism-related behavior in infants at risk of ASD.