A longitudinal study explored changes in symptom severity among young boys and girls with autism. The study, published in the Journal of Autism and Developmental Disorders, found that nearly 30% of the children showed less severe symptoms at age 6 than they had at age 3. Girls with autism were more likely to experience a decrease in symptom severity compared to boys and less likely to experience an increase in symptom severity.
Autism Spectrum Disorder (ASD) is a developmental condition characterized by persistent difficulties with communication, social skills, and repetitive behaviors. Autism is considered a spectrum disorder since symptoms vary largely across individuals, with symptom severity ranging from mild to severe. Researchers Einat Waizbard-Bartov and her team were motivated to conduct their study given the lack of consistent findings concerning symptom severity changes among children with autism.
While some studies suggest that most children with autism tend to show stable symptoms over time, there is increasing evidence that many children demonstrate substantial changes in symptom severity. Identifying these different trajectories could help pinpoint markers for which children with autism are likely to experience increasing, decreasing, or stable symptoms. Importantly, such insight could help clinicians identify which children would benefit from which intervention program.
Waizbard-Bartov and her colleagues collected data from 125 children with autism who were part of a larger longitudinal study called the Autism Phenome Project. The sample included 86 boys and 36 girls.
At around 3 years of age and again at age 6, the children were assessed for autism symptom severity and cognitive ability (IQ). Adaptive functioning was also assessed, which included scores for socialization, communication, motor skills, and daily living skills. The assessments were administered or supervised by trained clinicians specializing in ASD.
The researchers calculated the extent that each child’s symptom severity changed from the initial assessment to the follow-up, assigning each child a severity change score. This resulted in three different groups: a stable severity group whose severity scores changed by no more than 1 point (54%), a decreasing severity group whose scores decreased by 2 or more points (29%), and an increasing severity group whose scores increased by 2 or more points (17%). The researchers say these findings are in line with recent studies that suggest that a large number of children with autism experience changes in symptom severity, noting that around 46% of their subjects showed significant changes.
The research team next looked for characteristics that might differentiate the three groups. Notably, intervention histories did not differ significantly between the three groups.
However, the decreasing severity group included a disproportionate number of girls. This group also had more children with higher average IQs at both baseline and follow-up, and more children with greater adaptive functioning at follow-up. The increasing severity group, on the other hand, had a disproportionately low number of girls, as well as lower average IQ scores and reduced adaptive skills over time. Finally, the stable severity group had an equal ratio of boys and girls, stable adaptive skills, and tended to show increases in IQ with time.
The current understanding of autism tends to assume that girls with autism experience more impairment than boys. The study authors say it is therefore surprising that the girls in their study were more likely than the boys to experience a decrease in symptom severity and less likely to see an increase. This unexpected finding may have to do with the fact that girls with autism are more likely to “mask” their symptoms — a coping strategy that involves hiding one’s symptoms in social settings. It could be that the young girls in their study were already learning to camouflage their symptoms, creating the illusion that their symptoms were declining.
The authors intend to explore further longitudinal associations in future follow-ups and hope to gain more insight on why girls and boys with autism might present with different symptom severity trajectories.
The study, “Trajectories of Autism Symptom Severity Change During Early Childhood”, was authored by Einat Waizbard‑Bartov, Emilio Ferrer, Gregory S. Young, Brianna Heath, Sally Rogers, Christine Wu Nordahl, Marjorie Solomon, and David G. Amaral.