Feb. 20, 2004 -- Intriguing early research suggests that people with a genetic intolerance to gluten may also be at increased risk for schizophrenia. Investigators say the link, if proven, could lead to new treatment options for a small subset of schizophrenic people.
Using a Danish health registry, researchers from John's Hopkins University's Bloomberg School of Public Health found people with the genetic digestive disorder known as celiac disease to be three times as likely as the general population to develop schizophrenia. Lead researcher William W. Eaton, PhD, says the next step is to determine if following a gluten-free diet makes a difference in the symptoms of schizophrenic people with celiac disease. He estimates that 3% of schizophrenic people could potentially benefit from such a diet.
Celiac disease is a lifelong (chronic) condition in which foods that contain gluten damage the small intestine. Gluten is a form of protein found in some grains (notably wheat, barley, and rye). The damage to the intestine makes it hard for the body to absorb nutrients, especially fat, calcium, iron, and folate, from food.
"We can now screen for celiac disease, so it is at least conceivable that we can locate the folks with schizophrenia for whom gluten withdrawal might work," he tells WebMD. "But we still have to do those studies."
More Study Needed
Eaton and colleagues examined the medical histories of 7,997 schizophrenics admitted to a Danish psychiatric facility between 1981 and 1998. For each case they identified 25 people without the mental disorder, matched by sex and year of birth.
The researchers found no differences in the rates of other digestive disorders such as Crohn's disease and ulcerative colitis between the groups, yet people with schizophrenia were 3.2 times as likely to have a history of celiac disease as the comparison group. The findings are reported in the Feb. 21 issue of the British Journal of Medicine.
It is estimated that about 1% of the population of the U.S. has celiac disease. Eaton says he hopes to identify a group of people with schizophrenia who also have celiac disease and then put some of them on gluten-free diets to determine if the intervention is of therapeutic value.
Many Different Causes
He says the latest findings support the growing belief that schizophrenia has many different causes.
"The thinking is that instead of finding the magic gene or an environmental influence that is responsible for most cases, we will find dozens and maybe a hundred causes that each may each explain a small percentage of cases," he says.
Schizophrenia researcher William T. Carpenter, MD, of the University of Maryland, says it is now almost certain that no single gene will be implicated as the cause of the disease. He adds that seven different genotypes have been linked to schizophrenia so far and others are likely to be discovered. Carpenter is director of the Maryland Psychiatric Research Center at the University of Maryland.
The thinking is that genetically susceptible people develop schizophrenia when they are exposed to certain environmental triggers. Environmental influences that have been linked to the mental disorder include pregnancy problems, particularly in the second trimester; difficult delivery; having a father who is older; and the use of certain recreational drugs.
"For example, you may have a situation where a person has eight vulnerability genes and their mother had the flu in mid-trimester," Carpenter tells WebMD. "That double hit just might increase the likelihood of developing schizophrenia."