New research has found a link between a history of Candida yeast infections and mental illness.
In a study prompted in part by suggestions from people with mental illness, researchers at Johns Hopkins University found that a history of Candida yeast infections was more common in a group of men with schizophrenia or bipolar disorder than in those without these disorders.
The study also found that women with schizophrenia or bipolar disorder who tested positive for Candida performed worse on a standard memory test than women with schizophrenia or bipolar disorder who had no evidence of a past yeast infection.
The researchers caution that their findings do not establish a cause-and-effect relationship between mental illness and yeast infections. However, the findings may support a more detailed examination into the role of lifestyle, immune system weaknesses and gut-brain connections as contributing factors to the risk of psychiatric disorders and memory impairment, they noted.
“It’s far too early to single out Candida infection as a cause of mental illness or vice versa,” said Emily Severance, Ph.D., assistant professor of pediatrics and member of the Stanley Division of Developmental Neurovirology at the Johns Hopkins University School of Medicine. “However, most Candida infections can be treated in their early stages, and clinicians should make it a point to look out for these infections in their patients with mental illness.”
She adds that Candida infections can also be prevented by decreased sugar intake and other dietary modifications, avoiding unnecessary antibiotics, and improved hygiene.
Candida albicans is a yeastlike fungus naturally found in small amounts in human digestive tracts, but its overgrowth in warm, moist environments causes burning, itching symptoms, thrush (rashes in the throat or mouth) in infants and those with weakened immune systems, and sexually transmittable genital yeast infections in men and women. In its more serious forms, it can enter the bloodstream. In most people, the body’s own healthy bacteria and functioning immune system prevent its overgrowth.
The research team focused on a possible association between Candida susceptibility and mental illness in the wake of new evidence suggesting that schizophrenia may be related to problems with the immune system, and because some people with weakened immune systems are more susceptible to fungal infections, according to Severance.
She added that patients and parents of patients had shared stories and testimonials with the researchers about their experience with yeast infections, and these discussions prompted the investigation into possible links between mental illness and the microbiome, the body’s natural collection of bacteria. The researchers chose to focus on Candida because it is one of the most common types of yeast in the body, Severance explained.
For the study, colleagues from the Sheppard Pratt Health System took blood samples from 808 people between the ages of 18 and 65. This group was made up of 277 people without a history of mental disorder, 261 individuals with schizophrenia, and 270 people with bipolar disorder.
The researchers used the blood samples to quantify the amount of IgG class antibodies to Candida, which indicates a past infection with the yeast.
After accounting for factors like age, race, medications and socioeconomic status, which could skew the results, they looked for patterns that suggested links between mental illness and infection rates.
Significantly, it found no connection between the presence of Candida antibodies and mental illness overall in the total group, according to the researchers.
But when they looked only at men, they found 26 percent of those with schizophrenia had Candida antibodies, compared to 14 percent of the healthy males.
There wasn’t any difference found in infection rate between women with schizophrenia (31.3 percent) and the control group (29.4 percent).
The higher infection rate percentages in women over men likely reflects an increased susceptibility for this type of infection in all women, the researchers noted.
Men with bipolar disorder had clear increases in Candida as well, with a 26.4 percent infection rate, compared to only 14 percent in healthy males.
After accounting for additional variables related to lifestyle, the researchers found that the association between men with bipolar disorder and Candida infection could likely be attributed to homelessness. Many people who are homeless are subjected to unpredictable changes in stress, sanitation and diet, which can lead to infections like those caused by Candida.
However, the link between men with schizophrenia and Candida infection persisted and could not be explained by homelessness or other environmental factors, they said.
Severance said the data add support to the idea that environmental exposures related to lifestyle and immune system factors may be linked to schizophrenia and bipolar disorder, and that those factors may be different for each illness.
Similarly, specific mental illnesses and related symptoms may be very different in men versus women, she noted.
The research group, led by Robert Yolken, M.D., director of the Stanley Division of Developmental Neurovirology, had previously shown that toxoplasmosis infection could trigger schizophrenia, and this could lead to neurocognitive problems.
The organism that causes toxoplasmosis is a parasite that uses cats as its primary host, but it can also infect humans and other mammals.
To determine whether Candida infection affected any neurological responses, all participants in the new study took a 30-minute assessment of cognitive tasks to measure immediate memory, delayed memory, attention skills, use of language and visual-spatial skills.
Each of the five skills tests are scored based on an adjusted 100-point system.
Results showed that men and women in the control group with and without prior Candida infection had no measurable differences in scores in the five neurological responses.
However, the researchers noticed that women with schizophrenia and bipolar disorder who had a history of Candida infection had lower scores on the memory portions of this test compared to those women with no prior infection.
For example, women with schizophrenia and the highest Candida antibody levels scored about an average of 11 points lower on the test for immediate memory than the controls, from a score of 68.5 without infection to 57.4 with infection.
And the women with schizophrenia and the highest Candida antibody levels scored almost 15 points lower on the test for delayed memory, from a score of 71.4 without infection to 56.2 with infection.
The effect of Candida infection in women with bipolar disorder on memory test scores was smaller than that seen in women with schizophrenia, but was still measurable, according to the researchers.
“Although we cannot demonstrate a direct link between Candida infection and physiological brain processes, our data show that some factor associated with Candida infection, and possibly the organism itself, plays a role in affecting the memory of women with schizophrenia and bipolar disorder, and this is an avenue that needs to be further explored,” Severance said.
The study, supported by a research grant from the National Institute of Mental Health and a grant from the Stanley Medical Research Institute, was published in npj Schizophrenia, a new publication from Nature Publishing Group.