By E.J. Mundell
And young adults with autism who were relatively high-functioning -- meaning they did not have intellectual disabilities -- were actually at higher risk of depression than people with more severe forms of autism, British researchers found.
In the study, this higher-functioning subgroup was more than four times as likely to suffer from depression, compared to people without autism.
People with autism without intellectual disabilities "may be particularly prone to depression because of greater awareness of their difficulties," the researchers theorized.
The study was led by Dheeraj Rai, of the University of Bristol. His team published the findings online Aug. 31 in JAMA Network Open.
According to one U.S. expert, the findings mirror what many in the autism field have seen.
"Given the considerable social struggles that individuals with an autism spectrum disorder experience, it is not surprising that they are at significantly increased risk for depression," said Dr. Andrew Adesman. He directs developmental and behavioral pediatrics at Cohen Children's Medical Center in New Hyde Park, N.Y.
In the study, Rai's group looked at data that tracked almost 224,000 Swedes living in a particular county between 2001 and 2011. A total of 4,073 had been diagnosed with an autism spectrum disorder.
Tracking the participants' mental health, the study found that by their mid-to-late 20s, 19.8 percent of people with autism had a history of depression, compared to just 6 percent of those in the general population.
Not all of the increase in risk for depression was caused by genetics, Rai's group added, because people with autism still had double the odds for depression compared to a full sibling who did not have the disorder. That suggests that something other than DNA -- perhaps the stress of living with autism -- may play a role in depression risk.
The finding that autism without intellectual disability carried higher odds for depression highlights the need for earlier diagnosis, the researchers said.
"Many individuals with autism spectrum disorder, especially those without cognitive impairments, receive a delayed diagnosis, often after experiencing other psychiatric problems," the study authors wrote.
That can take a big psychological toll, perhaps contributing to depression risk, Rai's team suggested.
"Individuals receiving a diagnosis of autism spectrum disorder later in life often report long-standing stress in relation to social isolation, bullying, exclusion, and the knowledge they are different without the explanatory framework of [a diagnosis of] autism spectrum disorder," the researchers pointed out.
So, an early diagnosis could help lower depression risk, the investigators theorized, by giving young people with autism a context in which to better understand their "difference" and how to deal with it.
Dr. Peng Pang directs child and adolescent psychiatry at Staten Island University Hospital in New York City. Pang said the new study "underscores the public health significance of depression in autism spectrum disorders, and should prompt providers and caregivers to screen for and more actively treat depression in this population."
Peng also believes more research is needed to tease out the experiences and stigmas that may contribute to depression in young people with autism.