People with an autoimmune disease have almost twice the risk of developing an affective disorder, which includes depression, anxiety, and bipolar disorder, according to a new study. The findings provide more evidence of a link between inflammation and mental illness.
Previous research has indicated that there’s a link between inflammation and psychiatric disorders such as depression and bipolar disorder. Inflammation is thought to be a driving force behind autoimmune diseases, in which the immune system mistakenly attacks the body’s own healthy cells.
A new study led by the Center for Clinical Brain Sciences at the University of Edinburgh in Scotland investigated whether having an autoimmune disease was linked to a higher risk of mental health issues, specifically depression, anxiety, or bipolar disorder (collectively known as affective disorders).
The researchers obtained data from 1,563,155 adults living in the UK who were part of the Our Future Health study cohort. Participants were split into two groups: 37,808 individuals with a self-reported lifetime diagnosis of one of six autoimmune diseases, and 1,525,347 without such a diagnosis. The autoimmune diseases included were rheumatoid arthritis, Graves’ disease, inflammatory bowel disease, lupus, multiple sclerosis, and psoriasis. The presence of an autoimmune disease was used as a proxy for chronic inflammation in the absence of direct measurements of participants’ inflammatory markers.
People with autoimmune conditions were almost twice as likely to report having had depression, anxiety, or bipolar disorder at some point in their lives compared to people without these conditions (28.8% vs 17.9%). The autoimmune group also had higher levels of current depression and anxiety symptoms. Depression was reported by 18.6% compared with 10.5% in the general population; anxiety was 19.9% versus 12.9% in the general population. These results held true even after adjusting for factors like age, sex, ethnicity, income, chronic pain, family history of mental illness, and social isolation. Women with autoimmune conditions were found to have significantly higher rates of affective disorders than men with the same physical conditions.
The study’s findings suggest some practical steps that could be taken to address the problem. First, regular mental health screenings should be part of standard care for people with autoimmune diseases, especially women. The integration of mental health supports into treatment plans might help detect and manage affective disorders in this high-risk group. Additionally, healthcare professionals may need to pay particular attention to the psychological well-being of patients managing chronic inflammatory diseases.
The study does have limitations. Importantly, because this study was observational and not experimental or longitudinal, it cannot prove that autoimmune diseases cause mental illness, or vice versa. The use of self-reported data can introduce bias or inaccuracy. Autoimmune diseases were used as an indirect marker of chronic inflammation, rather than direct measures using inflammatory biomarkers, such as interleukin-6 (IL-6). It wasn’t possible to tell whether mental health issues came before, after, or at the same time as the autoimmune conditions. Because the data used was from people living in the UK, the findings may not apply to other countries.
Despite the obvious limitations of the study, it does strengthen the evidence linking chronic inflammation, via autoimmune disease, to a higher risk of affective mental health disorders. While more research is needed to untangle the exact mechanisms and timelines, the findings suggest a need for integrated mental and physical healthcare in people with autoimmune conditions.
The study was published in the journal BMJ Mental Health.