Largest study to date finds autism alone does not increase risk of violent offending

The study analysed data from 295,734 individuals in Stockholm County, Sweden, of whom 5,739 had a diagnosis of autism. The researchers tracked these individuals for violent crime convictions between ages 15 to 27 years using records from the Swedish National Crime Register.

The team, led by researchers at University of Bristol's Population Health Science Institute and the Karolinska Institute in Stockholm, found that individuals diagnosed with autism initially appeared to have a higher risk of violent offending. However, this risk was significantly reduced once the presence of additional attention-deficit/ hyperactivity disorder (ADHD) or conduct disorder were taken into account.

The study reported that having these co-occurring conditions, along with other, later-onset psychiatric disorders and alcohol and drug misuse, were the most important individual predictors of violent criminality in autism, not autism by itself.

Interestingly, when researchers considered individuals with ADHD or conduct disorder, an additional diagnosis of autism was actually found to reduce the risk of violent criminality, compared to individuals with ADHD or conduct disorder alone.

Dr Ragini Heeramun, Consultant Forensic Psychiatrist at the Avon & Wiltshire Partnership NHS Mental Health Trust in Bristol, said: "We know that some people with an autism diagnosis have challenging behaviour and may come into contact with the criminal justice system, however, whether having autism increases the risk of violence or not has previously not been clear."

"Our findings, from the largest study to date, show that at the population level, autism in itself doesn't seem to be associated with convictions for violent crimes. However, other conditions, such as ADHD, which can co-occur with autism, may increase such risks."

Dr Dheeraj Rai, Consultant Senior Lecturer in Psychiatry at the University of Bristol, said: "Interestingly, the additional presence of an autism diagnosis with attention-deficit/ hyperactivity disorder (ADHD) or conduct disorder was actually associated with a relatively lower risk of convictions, compared to having these conditions without autism.

"These findings are important for autism services, which often focus on providing a diagnosis of autism, rather than the identification of, and support for, the conditions that commonly occur alongside it."