At first glance, the symptoms of autism and obsessive-compulsive disorder (OCD) seem to have little in common. However, OCD rituals can reflect the repetitive behavior found commonly in autism.

These diagnoses often overlap in patients. Often, given a diagnosis for autism, a diagnosis for OCD will come later in life, and vice versa.

Associate professor of psychiatry, Suma Jacob, talked with Scientific American about how, just 10 years ago, virtually no one studied autism and OCD together.

Jacob explained how advisers would react when she said she wanted to research both conditions: “Top advisers in the field said, 'You have to pick one.'”

However, this is now changing in part because researchers have come to appreciate how many people have both conditions. Jacob and her colleagues are working to track the appearance of repetitive behaviors linked to either autism or OCD by age 3 in thousands of children. “From the brain perspective, these [conditions] are all related,” she says.

Edited for clarity