Some of the same health disparities also have been found in autistic children, but there's little research on whether they persist into adulthood or if new ailments develop.
"This new study makes a vitally important contribution by helping to map this little-explored territory," said Paul Shattuck, a Drexel University autism researcher who was not involved.
The study was prepared for release Wednesday at the International Meeting for Autism Research in Atlanta. It's based on medical records for 2,100 adults with autism spectrum disorder, an umbrella term encompassing mild autism and the more classic form of the disorder. They were enrolled during 2008-12 in a Kaiser health plan in northern California. Their records were compared with 21,000 non-autistic Kaiser enrollees.
Key results for autistic versus non-autistic adults:
—Depression: 38 percent vs. 17 percent.
—Suicide attempts: 1.6 percent vs. .3 percent.
—High blood pressure: 27 percent vs. 19 percent
—Cholesterol problems: 26 percent vs. 18 percent.
—Obesity: 27 percent vs. 16 percent.
—Alcohol use: 23 percent vs. 53 percent
—Smoking: 16 percent vs. 30 percent.
Autism expert David Mandell, director of a mental health policy center at the University of Pennsylvania, said research is needed to determine if autistic adults are more likely to be diagnosed with other conditions simply because they have more contact with doctors. But Mandell said the disparities are probably real and that the medical community tends to focus mostly on treating behavioral problems in autism. The study highlights a need to focus equally on "these very important health conditions," many of which are preventable, he said.
The government's latest statistics suggest that 1 in 68 U.S. children have autism, or more than 1 million Americans. It's considered a lifelong disorder that can involve language, intellectual and social impairments and unusual, repetitious behaviors.
Some common features, including lack of eye contact and social awkwardness, might suggest that people with autism dislike human contact. But Croen said it's more likely that they share a desire to connect with other people but have trouble doing so. That isolation could lead to problems like depression, she said.
Croen said isolation might also at least partly explain the lower rates of drinking and smoking, since those are social activities.