Silent condition: Anxiety in autistic people often goes undiagnosed.

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Adults with autism are more than twice as likely as neurotypical people to be diagnosed with an anxiety disorder, a new study suggests¹. Their non-autistic siblings are also more likely than the general population to receive an anxiety diagnosis.

The study is among the largest to probe the prevalence of anxiety in autistic adults. And unlike many earlier studies, it looks at specific anxiety disorders, such as post-traumatic stress disorder and panic disorder^2,3.

Little is known about the prevalence of these conditions among adults with autism, says Dheeraj Rai, consultant senior lecturer in psychiatry at the University of Bristol in the United Kingdom. “We are still very far behind in terms of how we measure [anxiety] in autistic adults.”

The new study also underscores the need for clinicians and caregivers to monitor anxiety in autistic adults.

“Anyone working with autistic people ought to be looking at anxiety carefully,” says Mikle South, professor of psychology and neuroscience at Brigham Young University in Provo, Utah, who was not involved with the work.

High anxiety:

Rai and his colleagues studied the health records of adults aged 18 to 27 in the Stockholm Youth Cohort. Of the 221,694 people they sampled, 4,049 have an autism diagnosis.

The team cross-referenced the health records with registries of people who have psychiatric diagnoses to identify adults with anxiety disorders.

They found that 20 percent of the autistic adults have an anxiety disorder, compared with less than 9 percent of the typical adults. Nearly 3.5 percent of the autistic adults have obsessive-compulsive disorder and about 3 percent have social phobia, compared with about 0.5 percent of controls for each condition. The work appeared in October in the Journal of Autism and Developmental Disorders.

The differences may in fact be even bigger because anxiety often goes unrecognized in autistic people, experts say.

“Most of the tools to measure and diagnose anxiety have been developed on neurotypical populations, which leaves the rest of us wondering how reliable and valid they are in people with autism,” says John Herrington, assistant professor of child psychiatry at the University of Pennsylvania, who was not involved in the research.

Family factors:

The fact that non-autistic siblings of autistic adults also have higher odds of anxiety than the general population suggests that genes or shared environmental factors may contribute to the overlap between the two conditions, the researchers say.

Anxiety diagnoses are most common among autistic adults of average intelligence or above. This may be because anxiety can be especially difficult to diagnose in adults with intellectual disability, who may be minimally verbal.

“Being able to diagnose anxiety requires someone to tell you about it,” South says. “If there’s low language, there’s going to be much less ability to report the anxiety.”

The new results parallel those of a previous study of the Swedish cohort, in which the same team found higher odds of depression among autistic adults of average intelligence or above than among those with below-average intelligence.

The next step, researchers say, is to understand why anxiety is so prevalent among autistic people, and to find better ways to assess and treat it.