"For all major symptoms, the percentage of people who improved was always greater than the percentage who worsened," Shattuck says. "If there was significant symptom change over time, it was always in the direction of improvement, though there was always a group in the middle that showed no change. The mean never went down."
Like most people, individuals with developmental disabilities such as autism continue to grow and change over time, Shattuck explains: "Their development is not frozen in time and forever the same. That's just not the case."
The paper reported on changes in broad categories of typical autistic symptoms: impaired verbal and nonverbal communication, impaired social interaction, and repetitive behaviors. Within those broad categories, changes across 32 specific symptoms - ranging from reciprocal conversation and interest in people to compulsions and rituals - were measured. Also examined were broader maladaptive behaviors such as aggression and self-injury that are not specific to autism. Across all categories, the proportion of study participants who improved was larger than the proportion that worsened.
Of those in the study, 69 percent were also classified as having mental retardation.
"Not everyone on the autism spectrum is mentally retarded," Shattuck says, "but being mentally retarded reduces the likelihood of improvement for many symptoms."
Why some in the sample improved is being investigated as part of the ongoing study, according to Shattuck.
"Our study demonstrates that significant changes are occurring," he explains. "But in terms of the underlying biological mechanisms, we don't yet know what's going on."
|Contact: Paul T. Shattuck|
University of Wisconsin-Madison