Autism Severity Can Change During Childhood

August 10, 2020

New Study Looks at Symptom Trajectories

Does the degree of severity of autistic symptoms remain static during preschool and early elementary school years? If a change in severity is experienced, could the degree of variation be influenced by initial severity levels, sex, IQ or level of adaptive functioning? These thought-provoking questions were recently posed by a new study out of the MIND Institute at UC Davis.

The institute’s new study Trajectories of Autism Symptom Severity Change During Early Childhood was published this spring in the Journal of Autism and Developmental Disorders. This novel research found that significant changes in autism severity are possible in the very young, especially if early intervention programs were utilized. For this study, 125 children (89 boys and 36 girls) with autism spectrum disorder (ASD) were utilized. The participants came from the Autism Phenome Project (APP), a longitudinal project in its 14th year at UC Davis.

Using the 10-point Autism Diagnostic Observation Schedule Calibrated Severity Score (ADOS CSS), recognized as the best tool for assessing autism impact levels, the researchers computed changes in the participants’ autism severity levels starting at age 3 through age 6. If the children’s autism symptoms increased or decreased by two points or more, the change was considered significant.

Three different groups were identified once severity levels were measured using the ADOS CSS. The Stable Severity Group, exhibiting symptoms that remained unchanged, was the most common group (54.4%). They were followed by Decreased Severity Group (28.8%), who showed less severe symptoms. The Increased Severity Group was the least common (16.8%). The identification of these three distinct groups indicated that almost half of the children’s symptom severity change with age. On a positive note, some children improved. On a sad note, some children’s autism symptoms worsened over time.

David Amaral, senior author and faculty member at the UC Davis MIND Institute addresses this issue in an article posted by Science Daily, “We found that nearly 30% of young children have less severe autism symptoms at age 6 than they did at age 3. In some cases, children lost their autism diagnoses entirely.”

Amaral continued, “It is also true that some children appear to get worse. Unfortunately, it is not currently possible to predict who will do well and who will develop more severe autism symptoms and need different interventions.”

Interestingly, seven of the children (four girls and three boys) had lost enough symptoms that they no longer met the criteria of an autism diagnosis. The study referred to this phenomenon as “optimal outcome.”

Additionally, the study showed that girls are more capable of decreasing severity than boys. Girls are also less likely to exhibit an increase in autism severity. The research team believes a possible explanation for this trend is the ability for girls to camouflage their symptoms, especially in social situations, showing higher adaptive functioning than boys.

In the end, the researchers found that IQ was the clearest predictor of symptom severity for children with ASD. If the subject’s IQ scores increased over the three observable years, the level of autism severity decreased.

The MIND Institute’s scientists found an answer for nearly all the questions posed at the beginning of their study. The team proved that autism severity can change in both a positive and negative way during early childhood. They also found that the young girls’ ability to use adaptive functioning skills typically resulted in better outcomes than the boys.

Unfortunately, one question eluded the MIND Institute scientists. They could not identify a relationship between early severity levels and future symptom change. In fact, the group of children with increased severity at age 6 had significantly lower severity levels at age 3. This discovery came as a surprise. The researchers call for more investigation into this finding in the future.


Einat Waizbard‐Bartov, Emilio Ferrer, Gregory S. Young, Brianna Heath, Sally Rogers, Christine Wu Nordahl, Marjorie Solomon, David G. Amaral. Trajectories of Autism Symptom Severity Change During Early Childhood. Journal of Autism and Developmental Disorders. May 2020.

Lisa D Wiggins, Brian Barger, Eric Moody , Gnakub Soke, Juhi Pandey, Susan Levy. Brief Report: The ADOS Calibrated Severity Score Best Measures Autism Diagnostic Symptom Severity in Pre-School Children. Journal of Developmental Disorders. July 2019.

Autism Severity Can Change Substantially During Early Childhood. Science Daily. May 28, 2020.

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