Women with a history of depression have something else to think about, as a newly released study showed that those falling into this category were two times more likely to develop systemic lupus erythematosus (SLE) when compared to those without depression.
Andrea L. Roberts, PhD, of Harvard T. H. Chan School of Public Health, led a study that examined data from two large cohorts of women to figure out if there was a correlation between depression and risk for SLE.
“There was a suspicion that depression might increase risk of autoimmune disease, including lupus, because among those with autoimmune diseases there’s a much higher rate of depression than in the general population,” she says. “Also, among people with autoimmune diseases, if they are also depressed, their symptoms tend to be worse.”
But there hadn’t been many studies that looked at people over time to see whether those who don’t have the disease that were depressed were more likely to get a new diagnosis. That’s what led to Roberts’ paper.
Behind the numbers
The data came from two large cohorts of women—the Nurses’ Health Study I and II. Overall, 145 cases of SLE among 194,483 women were examined. The findings showed that women with a history of depression were twice as likely to develop subsequent SLE compared with women without depression.
“What we found adds to the evidence that we already have that depression may cause an increase in the risk of lupus,” Roberts says. “There have been other studies that look at other autoimmune diseases such as psoriasis and Crohn’s disease. We know that depression causes people to have some biological inflammation and that is suspected to increase risk for autoimmune diseases.”
In the context of lupus, Roberts notes there are very few known risk factors, and it was somewhat surprising that the association with depression resulted in such large numbers. After all, she says, cigarette smoking only has a slight effect.
Additionally, in the study, Roberts and her team looked at whether other factors, such as cigarette smoking, BMI, oral contraceptive use, hormone use, alcohol use or diet, made women more prone to SLE for those with and without depression.
The research team also examined the association of depression status lagged by an additional four years, to lower the chance that associations occurred because SLE caused depression or because depression was an early symptom of SLE.
“We thought maybe people with lupus that hadn’t been diagnosed yet are depressed because of either their lupus symptoms or depression could even be a symptom of lupus, because it affects the brain, and there’s a lupus headache, so we were trying to be careful to reduce the possibility of reverse causation,” Roberts says. “We did a lot of analysis to put some time between when they got a depression diagnosis or when they reported they began taking an antidepressant, and when they reported a diagnosis of lupus.”
The findings can hopefully aid in early detection of lupus, as the screening of patients with depression or a family history of depression may alert doctors of the autoimmune disease earlier.
“I think people with lupus may be a bit skeptical about this, thinking that depression is just part of the condition,” Roberts says. “But we looked at depression in the first year of the study and lupus over the next 20 years and even that was predicting an increased risk, so we have a very big time lag between depression and the lupus.”
She admits, lupus is hard to diagnose and people are often misdiagnosed. However, Roberts says that if a patient is depressed, a physician might consider doing a screening for family history or autoimmune disease or just consider lupus as a possibility.
“This increases the emphasis for people with depression to try to improve their physical health behaviors,” Roberts says. “There are things you can do to reduce inflammation. You can improve your diet and exercise, and people with depression could try to tend to their physical health.”
Keith Loria is an award-winning journalist who has been writing for major newspapers and magazines for close to 20 years, on topics as diverse as sports, business, and healthcare.