Autistic behaviors, such as repetitive motions, problems interacting with others and impaired communication abilities, appear to change and improve as an individual ages, a new study shows.

The study, led by Marsha Mailick Seltzer, a Wisconsin professor of social work and the director of the UW-Madison Waisman Center, included more than 400 adolescents and adults with autism, half of which lived in Massachusetts and half in Wisconsin.

"On average, people are getting better," said Paul T. Shattuck, an assistant professor of social work at Washington University in St. Louis, in a news release.

"It is a hopeful finding, but the fact remains that those with severe autism will depend on others for their everyday needs and care for the rest of their lives," said Shattuck, who worked on the study as a graduate student and post-doctoral fellow at the University of Wisconsin-Madison's Waisman Center and is the first author of a paper on the findings.

For the study, which was published in the September Journal of Autism and Developmental Disorders, parents of autistic persons were interviewed every 18 months to assess changes in their child's symptoms and behaviors.

The study found that the symptoms of 241participants, initially aged 10- to 52-years-old, changed over a five-year period. Although symptoms for many in the study remained stable, a significant proportion exhibited improvements in symptoms and maladaptive behaviors.

Specificially, researchers observed changes across 32 specific symptoms — ranging from reciprocal conversation and interest in people to compulsions and rituals. 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, the authors reported. Autism affects an estimated one in 150 children and an unknown number of adults, the study’s authors said.