Older siblings tend to develop hyperactivity when raised in a home with an autistic younger sibling, a new study has found.

The research also showed that mothers of young, autistic children experience more depression and stress than mothers with typically developing kids.

While the impact on older siblings was not statistically significant, the trend may indicate the presence of symptoms associated with broader observable autism characteristics seen in previous studies, said Laura Lee McIntyre, a professor and director of the University of Oregon's school psychology program.

The new study gives a fresh look at autism's early effects on families by comparing control and experimental groups whose ages, education and socioeconomic situations were virtually identical.

Twenty families had a preschooler (ages 2-5 years old) diagnosed with autism and a typically developing older elementary school sibling (6-10); the control group of 23 families did not have an autistic child. Older children with diagnosed learning or mental disabilities were excluded.

The researchers looked closely at sibling adjustments, involving social, behavioural and academic performance as recorded by both parents and teachers, and at the well- being of the mothers, whose average age was 36 and 94-95 percent of whom were married. The median age of older siblings was seven and most were first- or second-graders.

"Contrary to what has been found by many researchers, we found that older siblings were pretty well adjusted, with no significant differences in parent-reported or teacher-reported social skills. These are all typically developing kids," said McIntyre.

Teachers, however, reported slightly more behavioural problems for the siblings of children with autism than control siblings.

The problems resembled hyperactivity but not at levels generally attributed to attention-deficit hyperactive disorder (ADHD). Teacher reports noted that these children exhibited slightly more fidgeting, movement and attention problems.

The study was published in the March issue of the journal Focus on Autism and Other Developmental Disabilities. (ANI)