Doctors at the University of North Carolina at Chapel Hill studied patient records for more than 30,000 children and found that rates of autism rose substantially if parents had suffered schizophrenia, depression or a range of other personality and psychiatric disorders.
The risk of autism went up 70% if 1 parent has a psychiatric disorder and twice as high if both parents has psychiatric disorders.

Julie Daniels, Head Researcher on the study.

Our research shows that mothers and fathers diagnosed with schizophrenia were about twice as likely to have a child diagnosed with autism. We also saw higher rates of depression and personality disorders among mothers, but not fathers,

The association was strongest when the parent had schizophrenia
and was less with depression or personality disorders.
The finding along with previous studies points to a genetic cause for autism

Daniels

The diagnosis of autism includes a wide spectrum of disorders that are probably caused by different things,
The more we can refine groups of individuals with the classification of autism, the better our ability to look for causes and treatments.
Knowing family history of psychiatric disorders is one way researchers might be able to refine the classification of autism. It indicates that a genetic trait may be involved. It may help identify opportunities to prevent or treat the disorder.

Source: Autism’s link to mental illness in parents