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Spectrum: Autism Research News

Clinical research: Autism development follows distinct paths

by  /  4 May 2012
THIS ARTICLE IS MORE THAN FIVE YEARS OLD

This article is more than five years old. Autism research — and science in general — is constantly evolving, so older articles may contain information or theories that have been reevaluated since their original publication date.

Speaking skills: Children with autism who have poor language ability, but no intellectual disability, are more likely to improve by adolescence than their peers with intellectual disability.

A fraction of children with autism show significant improvements in social and communication skills over time compared with their peers with the disorder, according to a study published 2 April in Pediatrics1.

The study also shows that, apart from these ‘bloomers,’ children tend to stay on a fixed developmental path: Those who are low-functioning at the time of diagnosis remain so at 14 years of age, and vice versa.

The researchers looked at case records from the California Department of Developmental Services of nearly 7,000 children with autism who had had at least four recorded health evaluations between the time of diagnosis and 14 years of age. They then used these records to track the children’s communication and social skills and their levels of repetitive behaviors over time.

Using statistical analysis, the researchers show that children’s scores on communication and social ability tests fit into six distinct developmental trajectories. Five of these trajectories remain separate from one another, meaning, for example, that children with autism who are higher-functioning than their peers at 3 years of age remain so at 14.

However, the amount of improvement they show differs for each trajectory. For example, children who have a higher skill level at the time of diagnosis improve more with time than those who are lower-functioning.

The sixth trajectory describes about ten percent of children with autism, those that show major developmental improvements. They score at the level of the lowest-functioning group at 3 years of age and near the highest-functioning group at 14.

Scores for repetitive behaviors are more stable, the study found, with only 15 percent of children — half of whom improved and half of whom worsened — showing changes over time.

Changes in each core autism domain — social and communication skills and repetitive behaviors — are also independent, the study found, so a child could show substantial improvement in social behavior, but not communication, for example.

The researchers also analyzed whether sociological factors had an impact on whether children are more likely to be in one group or another. Children from lower-income families, minority groups and those with less-educated mothers are more likely to be on a lower-functioning trajectory, the study found, and vice versa. Children who show significant gains in skills are less likely to have intellectual disability than the children whose skill levels matched their own at a young age. They are also more likely to have educated mothers who are not from a minority group.

Developmental differences among groups could be due to inequalities in access to services and treatments. Although other factors may influence the trajectory of autism, social factors show a strong statistical correlation, the researchers say. Further research is needed to better understand what factors can influence outcomes for children with the disorder.

References:

1: Fountain C. et al. Pediatrics Epub ahead of print (2012) PubMed