People diagnosed with autoimmune diseases experience mood and anxiety disorders at nearly twice the rate of the general population. Data from more than 1.5 million adults in the UK suggests that persistent physical inflammation is closely linked to this increased mental health risk. The study results were published in the journal BMJ Mental Health.
Medical professionals classify depression, anxiety, and bipolar disorder as affective disorders. These psychological conditions change a person’s mood, emotional state, and daily functioning. Autoimmune diseases have very different and visible symptoms that occur when the body’s immune system mistakenly attacks its own healthy tissue as if it were a foreign threat. Conditions such as rheumatoid arthritis, inflammatory bowel disease, and lupus cause chronic and widespread inflammation throughout the body.
In recent years, medical researchers have noticed a clear link between immune system activity and mental health outcomes. Blood markers that indicate an active immune response, such as certain proteins and cellular messengers, are often elevated in people experiencing depression or anxiety. Some studies even show that administration of standard antidepressants coincides with a reduction in these inflammatory markers.
Conversely, people with mood disorders may see a slight improvement in their symptoms when they receive treatments that are aimed solely at reducing inflammation in the body. Because of these distinct patterns, researchers believe that inflammation may play a direct biological role in the development or worsening of mental health conditions.
There are significant logistical hurdles to testing this idea at scale. Analyzing blood samples from thousands of people to quantify specific inflammatory proteins is prohibitively expensive and time-consuming. As a result, studies exploring the relationship between the immune system and the brain typically rely on very small groups of participants.
University of Edinburgh researcher Arish Mudra Rakshasa Roots and his colleagues decided to take an indirect approach to overcome this limitation. In the absence of direct blood measurements, having a diagnosed autoimmune condition can serve as a reliable indicator of chronic internal inflammation. The research team used a large national health database to see if simply living with one of these inflammatory diseases was associated with a person’s mental health history.
The researchers used the Our Future Health initiative. This database collects detailed survey information and physical health data from volunteer participants across the UK. The research team filtered records from about 1.5 million adults and divided them into two different groups for comparison.
One group consisted of approximately 38,000 people who reported having at least one of six autoimmune diseases. Researchers focused on rheumatoid arthritis, lupus, multiple sclerosis, psoriasis, inflammatory bowel disease, and Graves’ disease. The remaining 1.5 million adults served as a large control group representative of the general population without autoimmune diseases.
All participants completed a lengthy questionnaire regarding demographic background, family history, and lifestyle habits. They looked at whether a doctor or other health care professional had diagnosed them with depression, anxiety, or bipolar disorder at any point in their lives. The survey also asked whether participants’ biological parents had ever received a similar psychiatric diagnosis.
The survey included standard psychiatric rating scales to assess current mental health status along with past diagnoses. Participants answered several questions about their current mood, allowing researchers to compile scores for active depressive and anxiety symptoms.
The research team found significant differences in mental health history between the two groups. Just under 29% of people with autoimmune diseases report being diagnosed with an affective disorder during their lifetime. In contrast, approximately 18% of the general population reported a similar mental health history.
This pattern held true regardless of the exact autoimmune condition experienced by the participants. More than a quarter of participants with autoimmune diseases experienced depression, compared to 15% of general participants. Similarly, about 21 percent of the autoimmune group reported an anxiety disorder diagnosis, while only 12 percent of the control group said the same.
Although bipolar disorder remains relatively rare in the general population, there has also been a rise in bipolar disorder among people with overactive immune systems. Almost 1 percent of the autoimmune group reported having been diagnosed with bipolar disorder during their lifetime. This was approximately twice the prevalence seen among participants without immune status.
My current day-to-day symptoms paint a very similar picture. Almost 19 percent of the autoimmune group had mood questionnaire scores high enough to indicate active, ongoing depression, compared to only 10 percent of the general population. Reports of current anxiety were similarly high among the autoimmune group.
Other life situations can deeply impact mental health, so looking at raw percentages only tells part of the picture. People with autoimmune diseases often experience severe physical discomfort, and chronic pain is a major cause of poor mental health. Physical illness can make it difficult to leave the house and lead to social isolation, which can independently undermine mental stability.
The researchers built a mathematical model to adjust the data for these confounding variables. In addition to considering age, gender, ethnicity, and household income, researchers also took into account whether participants were living with chronic pain or reported seeing family and friends less frequently.
Even after removing the effects of pain, loneliness, and income, people with autoimmune diseases were still about 50 percent more likely to experience a mood or anxiety disorder. The researchers noted that this increased risk was similar for depression, bipolar disorder, and anxiety. This suggests that systemic inflammation may create systemic vulnerability to several different types of mood disorders, rather than causing one specific disorder.
The data also revealed clear differences based on biological sex. Both autoimmune diseases and affective disorders are recognized to occur more frequently in women. The study confirmed this trend, showing that female participants with an autoimmune diagnosis were significantly more likely to report mood and anxiety disorders than male participants with identical health conditions.
The medical literature offers several theories to explain these sex differences. The higher prevalence of autoimmune diseases in women may be related to differences in sex hormones, chromosomal factors, or differences in the way certain antibodies circulate in the blood. Additionally, the specific effects of the immune response on brain chemistry may be stronger in women, potentially compounding their risk for mental health problems.
Because this study relied entirely on observational data, the results cannot prove whether inflammation directly causes mental illness. The researchers were only able to identify numerical correlations between physical health exams and mental health outcomes.
The database did not include a specific timeline regarding when each participant received a specific diagnosis. It remains completely unclear whether autoimmune diseases develop before affective disorders or vice versa. In some cases, people experience severe depression years before their immune system starts attacking their joints and skin.
The study also relied entirely on self-reported health history. Unless actual medical records are accessed to confirm the diagnosis, findings are dependent on the accuracy of participants’ memories. A final psychiatric diagnosis usually requires a structured clinical interview with a doctor, but that wasn’t possible in the study of more than 1 million people.
Future studies will need to continue to follow participants over several years to determine the exact sequence of disease onset. Tracking symptoms over time may reveal whether a spike in physical inflammation coincides exactly with the onset of a depressed mood or anxiety state.
The authors hope to eventually incorporate direct biological measurements into large databases like Our Future Health. Analyzing actual blood samples to detect specific inflammatory proteins could help reveal whether the severity of a person’s internal inflammation matches the severity of their mood symptoms. This level of detail would provide a clearer picture of the biological mechanisms at play.
In clinical practice, these widespread patterns suggest that health care professionals should consider conducting regular mental health screenings for patients with autoimmune diseases. If symptoms of depression and anxiety are detected early, doctors may be able to provide tailored psychological support alongside standard physical treatments. Addressing both the immune system and mental health at the same time could improve the overall quality of life for millions of people.
The study, “Affective Disorders and Chronic Inflammatory Conditions: An Analysis of 1.5 Million Participants into Our Future Health,” was authored by Arish Mudra Rakshasa Roots, Duncan Swiffen, Christina Stein, Katie FM Marwick, and Daniel J. Smith.
