London, Jan 2 (IANS): People with certain genetic conditions are likely to have significant symptoms of autism such as social and communication difficulties or repetitive behaviours, even if they do not meet all diagnostic criteria, says an international study.

The study by researchers at Cardiff University suggests that clinical services need to adapt so that people diagnosed with autism-linked genetic conditions are not denied access to vital support and interventions.

Published in The American Journal of Psychiatry, the study analysed data from 547 people who had been diagnosed with one of four genetic conditions, also known as copy number variants (CNVs), associated with a high chance of autism -- 22q11.2 deletion, 22q11.2 duplication, 16p11.2 deletion and 16p11.2 duplication.

Copy number variants happen when a small section of a person's DNA is missing or duplicated. Certain CNVs have been linked to a range of health and developmental issues. They can be inherited but can also occur at random.

The results showed a high prevalence of autism in individuals with these four genetic conditions, ranging from 23 per cent to 58 per cent.

The prevalence of autism in the general population is one per cent.

Using clinical cut-offs, the team also found 54 per cent of people with these genetic conditions who did not meet full autism diagnostic criteria nonetheless had elevated levels of autistic symptoms.

There was also considerable variability in symptoms of autism between those who had the same genetic condition.

"Our study shows that an individualised approach is needed when assessing the needs of people with genetic conditions," said Samuel Chawner, based at Cardiff University's MRC Centre for Neuropsychiatric Genetics and Genomics.

"Although many of those who were included in this study would not have met all of the criteria which define someone as having autism, more than half of those with these genetic conditions had significant symptoms associated with it -- such as social and communication difficulties or repetitive behaviours."

Data for the study was pooled from eight clinical research centres around the world, which had used the "Autism Diagnostic Interview - Revised (ADI-R)" and IQ tests on study participants.

The ADI-R is used internationally in research as well as in clinical settings for making autism diagnoses. It involves an interview with the parent or guardian and asks about the child's developmental history across areas of social skills, communication skills and repetitive behaviours.