Symptoms of autism can change significantly during early childhood, according to a new study from the University of California (UC) Davis MIND Institute. In fact, the researchers found that nearly 30% of young children have less severe autism symptoms at age 6 than they did at age 3.
Previous research has shown inconsistent results in terms of changes in autism severity during childhood. The general sense was that the severity of autism at diagnosis would last a lifetime.
The study, published in the Journal of Autism and Developmental Disorders, looked at changes in symptom severity in early childhood and the potential factors linked to those changes. It involved 125 children (89 boys and 36 girls) with ASD from the Autism Phenome Project (APP), a longitudinal project in its 14th year at the MIND Institute. The children received substantial community-based autism intervention throughout their childhood.
The research team used a 10-point severity measure called the ADOS Calibrated Severity Score (CSS) derived from the Autism Diagnostic Observation Schedule (ADOS), the gold standard assessment tool in autism research. They calculated a severity change score for participants as the difference between their ADOS CSS scores at age 6 and at age 3. A change of two points or more was considered a significant change in symptom severity.
The researchers classified subjects based on their severity change score into a Decreased Severity Group (28.8%), a Stable Severity Group (54.4%) and an Increased Severity Group (16.8%). One key finding was that children’s symptom severity can change with age. In fact, children can improve and get better.
“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,” said David Amaral, a distinguished professor of psychiatry and behavioral sciences, faculty member at the UC Davis MIND Institute and senior author on the study.
“It is also true that some children appear to get worse,” Amaral said. “Unfortunately, it is not currently possible to predict who will do well and who will develop more severe autism symptoms and need different interventions.”
“Optimal outcome” occurs when someone previously diagnosed with ASD no longer meets autism diagnostic criteria due to loss of autism symptoms. In this study, seven participants (four girls and three boys) had an ADOS CSS below the ASD cutoff at age 6, potentially indicating optimal outcome. Children showing reduced symptom severity had better adaptive skills in multiple areas compared to those in the stable or increased severity groups.
Girls and boys might be characterized with different manifestations of autism symptoms. Girls might show better developmental results than boys in cognition, sociability and practical communication skills.
“We found that girls with autism decrease in severity more than boys and increase in severity less than boys during early childhood,” said Einat Waizbard-Bartov, a graduate researcher at the MIND Institute and the first author of the paper.
One possible explanation for this difference is the girls’ ability to camouflage or hide their symptoms, according to Waizbard-Bartov. Camouflaging the traits of autism includes masking one’s symptoms in social situations. This coping strategy is a social compensatory behavior more prevalent in females diagnosed with ASD compared to males with ASD across different age ranges, including adulthood.
“The fact that more of the girls appear to have decreased in autism severity may be due to an increasing number of girls compared to boys who, with age, have learned how to mask their symptoms,” Waizbard-Bartov said. “We will explore this possibility in future studies.”
The researchers also found that IQ had a strong association with change in symptom severity. Children with higher IQs were more likely to show a reduction in ASD symptoms.
“IQ is considered to be the strongest predictor of symptom severity for children with autism,” Waizbard-Bartov said. “As IQ scores increased from age 3 to age 6, symptom severity levels decreased.”
The research team could not identify a link between early severity levels and future symptom change. Surprisingly, the group of children with increased symptom severity at age 6 showed significantly lower severity levels at age 3, and their severity scores were less variable than the other groups.
The study raises several issues for further research, such as the relationships between IQ, initial severity level, and type and intensity of intervention received, in relation to symptom change over time.