Anxiety disorders "should be considered an important public health problem," write the researchers.
They included Jitender Sareen, MD, FRCPC, of Canada's University of Manitoba in Winnipeg.
In any given year, about 40 million U.S. adults experience anxiety disorders, according to the National Institute of Mental Health (NIMH).
It's normal to get butterflies every now and then. Anxiety disorders go way beyond that; they're much more severe and must last at least six months to be diagnosed.
Anxiety disorders include panic disorder, obsessive-compulsive disorder, posttraumatic stress disorder (PTSD), phobias, social anxiety disorder, and generalized anxiety disorder.
Treatments include counseling and medication.
Sareen's team studied more than 4,100 adults in Germany who were 18-65 years old.
Participants completed surveys about their mental and physical health, their quality of life, and any disabilities they'd had in coping with everyday life during the previous month.
They also got medical checkups.
People with anxiety disorders were more likely to have physical problems including thyroid disease, respiratory disease, gastrointestinal disease, arthritis, migraines, and allergies.
Anxiety disorders appeared to precede physical health problems, the study also shows.
Compared with people with physical health problems, those who also had anxiety disorders tended to report a worse quality of life and more days where they couldn't handle daily life.
The study didn't include PTSD. The results take social and economic factors into account.
Like depression, anxiety may raise the odds of developing physical health problems, the researchers note.
They call for programs "to recognize and treat anxiety disorders in the medically ill," noting that such programs are already in place for depression.
"During the last decade, efforts have been substantially increased to improve recognition and treatment of depression" in general medical practices, the researchers write.
"Similar efforts should strongly be considered for anxiety disorders," they continue.
The findings don't mean that everyone with anxiety disorders develops a physical illness.
Exactly how anxiety may lead to physical illness also remains a mystery.
Here are tips from the NIMH on getting help for anxiety disorders:
First, see your family doctor.
If your doctor diagnoses an anxiety disorder, the next step is usually seeing a mental health professional.
Choose a mental health professional you feel comfortable talking with, and work together to plan treatment.
If medication is part of your treatment, don't stop taking those drugs abruptly. Talk to your doctor first.
Stress management and support groups may also prove helpful.
Family members should support you in your treatment. If they aren't familiar with anxiety disorders, you may want to share material with them about your condition.
SOURCES: Sareen, J. Archives of Internal Medicine, Oct. 23, 2006; vol 166: pp 2109-2116. National Institute of Mental Health: "Anxiety Disorders." News release, JAMA/Archives.
By Miranda Hitti
Reviewed by Louise Chang