Stress may not just affect the mind, but may actually affect the physical immune system, a new study found.
Everyone will experience a significant life stressor at some point in their lives, such as the loss of a loved one or exposure to violence. While most people exposed to hardships gradually recover, a significant percentage develop severe psychiatric reactions like post-traumatic stress disorder (PTSD), acute stress reactions or adjustment disorder.
But the study, published Tuesday in the Journal of the American Medical Association, asked: Do psychiatric reactions to life stressors result in the physical dysfunction of the immune system?
Autoimmune disorders like celiac disease, Crohn’s disease, psoriasis and rheumatoid arthritis are conditions where the immune system mistakenly attacks the body, incorrectly sensing foreign invaders. The causes of autoimmune diseases are largely unknown, but genetic, infectious and environmental factors are thought to play a role. These immune diseases strike even the young, who haven’t experienced the stressors noted in this study.
To assess whether there was a connection between stressors and these autoimmune disorders, researchers from the University of Iceland looked at the medical records of 100,000 people with stress-related psychiatric disorders between 1981 and 2013 in Sweden and compared them to 120,000 of their siblings and nearly 1.1 million unrelated people who had no stress-related disorders. People with a stress-related psychiatric disorder in the study were, on average, diagnosed at age 41 and 40 percent were male.
Compared to those without stress-related disorders, they were at an increased risk of 41 different autoimmune diseases -- and patients with PTSD were at an increased risk of having multiple autoimmune diseases, including rheumatoid arthritis, psoriasis, Crohn’s disease and celiac disease.
The risk for all autoimmune diseases may not be equal: This study found a higher risk for celiac disease and lower for rheumatoid arthritis.
For patients with PTSD, taking antidepressant medications that block serotonin (SSRIs) was associated with a decreased risk of autoimmune disease, which "strengthens the evidence for the potential causal link between stress-related disorder and subsequent autoimmune diseases," lead author Dr. Huan Song told ABC News.
Previous studies have also shown a link between Vietnam War veterans with PTSD and a higher occurrence of autoimmune diseases. But more research is needed to understand why.
“We need more studies to inform the potential underlying mechanism behind the association," Song said, "for example exploring potential genetic and early environmental contributors and the effect of alternations in health-related behavior."
Overall, this study's findings suggest that stress can impair the body’s immune system, according to the researchers, and further research and in more places could help.
One explanation could be that a major life stressor can cause severe lifestyle changes like less sleep, more smoking and alcohol or substance abuse, less exercise and worse diet. In turn, those may contribute to the development of autoimmune disease.
This study was limited in a few ways. Autoimmune diseases may be underrepresented, because less severe autoimmune conditions managed by primary care doctors were not included in this study. This study was also done in Sweden and may not be applicable to other populations. In addition, it is a study of what researchers observed and they may not have known some of the natural differences that could explain the study findings.
The findings show an association between stressors and the immune system, but not that the psychiatric stressors caused the immune problems.
"The under-diagnosis and under-treatment of these studied stress-related disorders have been an issue discussed for many years," Song said. "Based on our results, patients suffering from severe emotional reactions after trauma, or other life stressors, should seek medical care to reduce their symptom burden and thereby also potentially reduce their future risk of further health decline."