A large study conducted in Sweden suggests that children from families with a history of brain conditions are more likely to have autism. The study found that the closer the relationship to family members with these conditions, the higher the chances of the child having autism. Previous studies have also reported similar trends, showing that a child’s odds of having autism increase if they have a sibling with autism, attention deficit hyperactivity disorder (ADHD), or intellectual disability, or if they have a parent with schizophrenia, depression, bipolar disorder, or anxiety.
The study examined family history of brain conditions, including epilepsy and others, and included grandparents, aunts, uncles, and cousins. Researchers used national registries to identify over 8 million relatives of 10,920 children with autism and 556,516 typical children enrolled in the Stockholm Youth Cohort. The study found that children with a first-degree relative (sibling or parent) with a brain condition other than autism had up to 4.7 times the usual odds of having autism. They also had up to 7.6 times the odds of having both autism and intellectual disability.
The study’s findings align with evidence linking risk factors for autism to those for other conditions. The risk of autism, with or without intellectual disability, decreases as the genetic distance between the child and the affected family member increases. This suggests the presence of a general liability factor that is genetically transmitted, contributing to various psychiatric and neurological disorders.
Children with an autistic parent or sibling have nine times the usual odds of having autism and 4.1 times the odds of having autism with intellectual disability. In comparison, children who have a parent or sibling with both autism and intellectual disability have 14.2 times the usual odds of having both conditions and 3.8 times the odds of having autism alone. These findings support the notion that the genetics of autism with intellectual disability differs from that of autism alone.
The researchers are conducting further analysis using records from national registries in Denmark to investigate the relationship between autism and family history of brain and other health conditions.