Parents’ mental illness raises risk of autism

Severe mental illness such as schizophrenia or bipolar disorder in a parent significantly ups autism risk.

By Emily Elert

8 August 2014 | 2 min read

This article is more than five years old.

Neuroscience—and science in general—is constantly evolving, so older articles may contain information or theories that have been reevaluated since their original publication date.

Having a parent with a severe mental illness such as schizophrenia or bipolar disorder significantly increases the risk of autism and attention deficit hyperactivity disorder (ADHD), according to a study published 23 May in Annals of Epidemiology.

The researchers analyzed the medical records of 870,017 children born in Sweden between 1992 and 2001 and those of their biological parents. After adjusting for factors such as sex, birth order, parental age, education and income, they found that severe mental illness in the mother increases a child’s risk of autism by about 70 percent and ADHD risk by about 55 percent. Mental illness in the father also increases risk of these disorders, by about 55 percent for autism and 35 percent for ADHD.

Some studies have shown that mothers with mental illness tend to to have birth complications. Others have found that preterm and underweight babies are more likely to develop autism than babies born full term at a healthy weight.

Together, these findings raised the possibility that parental mental illness, birth outcomes and autism are all linked.

The new study suggests that this is not the case: Adjusting for preterm birth and low birth weight had little effect on the risk of autism or ADHD that parental mental illness confers. This suggests that birth complications and parents’ mental illness are independent risk factors for autism.