Clinical research: Study finds four types of autism severity
Children with autism who have trouble with daily activities, such as brushing their teeth, and who lag on measures of cognition are the most likely to have persistently severe symptoms. The findings, based on a long-term study of children between 2 and 5 years of age, were published 2 August in the Journal of Autism and Developmental Disorders1.
The study investigated autism severity over time and identified four possible trajectories: persistently severe, persistently moderate, improving and worsening. These results replicate the findings of a 2012 study, which described the same four groups and found that 80 percent of 354 children had stable symptoms.
Both studies use the calibrated severity score, an adaptation of the Autism Diagnostic Observation Schedule (ADOS), a well-established diagnostic test for autism. The severity score controls for age and language ability, allowing researchers to compare symptoms among different ages.
In the new study, researchers recruited 129 children who had been diagnosed with autism. The researchers assessed each child four times, once a year, starting at 30 months of age. Of the 129 children, 101 completed at least three of the four assessments.
As in the previous study, 78 percent of the children had symptoms that were stable over time, with 47 in the persistently severe and 54 in the persistently moderate categories;10 children worsened over time and 18 of them improved.
Children in the persistently severe class had the most significant problems with daily living skills, such as brushing their teeth or dressing themselves, and had the lowest nonverbal cognition scores.
Age, gender, ethnicity and maternal education had no bearing on the severity of symptoms. Interestingly, children in the persistently severe class were the most likely to have undergone intensive behavioral intervention. This is probably because they would be more likely to qualify for these services under Medicare, the researchers say.
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1: Venker C.E. et al. J. Autism Dev. Disord. Epub ahead of print (2013) PubMed