Large-scale study links autoimmune diseases to higher rates of depression and anxiety

People diagnosed with autoimmune diseases experience mood and anxiety disorders at nearly double the rate of the general population. Data from more than 1.5 million adults in the United Kingdom suggests that persistent physical inflammation is closely tied to this elevated mental health risk. The findings were published in the journal BMJ Mental Health.

Medical professionals label depression, anxiety, and bipolar disorder as affective disorders. These psychological conditions alter a person’s mood, emotional state, and daily functioning. Autoimmune diseases have entirely different visible symptoms, occurring when the body’s immune system mistakenly attacks its own healthy tissues as if they were foreign threats. Conditions such as rheumatoid arthritis, inflammatory bowel disease, and lupus cause chronic, widespread inflammation throughout the body.

In recent years, medical researchers have noticed a distinct connection between immune system activity and mental health outcomes. Blood markers that indicate an active immune response, such as specific proteins and cellular messengers, frequently run high in individuals experiencing depression or anxiety. Some studies even show that administering standard antidepressant medications corresponds with a drop in these inflammatory markers.

Conversely, receiving treatments designed solely to lower bodily inflammation can sometimes result in modest improvements in symptoms for people with mood disorders. Because of these distinct patterns, researchers suspect that inflammation could play a direct biological role in creating or worsening mental health conditions.

Testing this idea on a grand scale presents major logistical hurdles. Analyzing blood samples to quantify specific inflammatory proteins in thousands of people is prohibitively expensive and time consuming. As a result, studies exploring the connection between the immune system and the brain typically rely on very small groups of participants.

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University of Edinburgh researcher Arish Mudra Rakshasa-Loots 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 serves as a reliable indicator of chronic internal inflammation. The team utilized a massive national health database to see if simply living with one of these inflammatory conditions relates to a person’s mental health history.

The researchers tapped into the Our Future Health initiative. This database collects detailed survey information and physical health data from volunteer participants entirely across the United Kingdom. The research team filtered the records of roughly 1.5 million adults, dividing them into two distinct groups for comparison.

One group consisted of nearly 38,000 individuals who reported having at least one of six autoimmune diseases. The researchers focused on rheumatoid arthritis, lupus, multiple sclerosis, psoriasis, inflammatory bowel disease, and Graves’ disease. The remaining 1.5 million adults served as a massive control group, representing the general public without autoimmune conditions.

All participants completed lengthy questionnaires concerning their demographic backgrounds, family histories, and lifestyle habits. They noted if a doctor or other medical professional had ever diagnosed them with depression, anxiety, or bipolar disorder at any point in their lives. The surveys also asked if the participants’ biological parents had ever received similar psychiatric diagnoses.

To gauge present mental health status alongside past diagnoses, the survey included standard psychiatric rating scales. Participants answered several questions about their current mood, allowing the researchers to tally scores for active depressive and anxious symptoms.

The team discovered a pronounced difference in mental health history between the two groups. Just under 29 percent of individuals with an autoimmune disease reported a lifetime diagnosis of an affective disorder. In contrast, roughly 18 percent of the general population group reported the same mental health history.

This pattern held true regardless of the exact autoimmune condition a participant experienced. Over a quarter of participants with an autoimmune disease had experienced depression, compared to 15 percent of the general public. Likewise, about 21 percent of the autoimmune group reported an anxiety diagnosis, whereas only 12 percent of the control group said the same.

While bipolar disorder remains relatively uncommon in the general public, it was also elevated among those with overactive immune systems. Almost one percent of the autoimmune group reported a lifetime bipolar disorder diagnosis. This was roughly double the prevalence found among the participants without immune conditions.

Current daily symptoms painted a very similar picture. Nearly 19 percent of the autoimmune group scored intensely enough on mood questionnaires to indicate active, ongoing depression, compared to just 10 percent of the general population. Reports of current anxiety were similarly elevated among the autoimmune group.

Looking at raw percentages only tells part of the story, as other life circumstances can deeply impact emotional well being. People with autoimmune diseases often experience severe physical discomfort, and chronic pain is a major contributor to poor mental health. Physical illnesses can also make it difficult to leave the house, leading to social isolation, which independently harms emotional stability.

The researchers constructed mathematical models to adjust their data for these confounding variables. In addition to accounting for age, sex, ethnicity, and household income, they factored in whether participants lived with chronic pain or reported a low frequency of visiting with family and friends.

Even after stripping away the influence of pain, isolation, and income, the odds of experiencing a mood or anxiety disorder remained about 50 percent higher for those with autoimmune diseases. The researchers noted that this elevated risk was broadly identical across depression, bipolar disorder, and anxiety. This suggests that systemic inflammation might create a generalized vulnerability to several different types of mood disruption, rather than causing one specific disorder.

The data also revealed clear differences based on biological sex. Autoimmune conditions and affective disorders are both recognized to occur more frequently in women. The study confirmed this trend, showing that female participants with autoimmune diagnoses reported notably higher rates of mood and anxiety disorders than male participants with the exact same physical health conditions.

Medical literature presents a few theories to explain these sex differences. The higher prevalence of autoimmune conditions in women might relate to differing sex hormones, chromosomal factors, or variations in how certain antibodies circulate in the blood. Additionally, the specific ways that immune responses affect brain chemistry might be stronger in women, leading to a compounded risk for mental health issues.

Because this study relied entirely on observational data, the results cannot establish whether inflammation directly causes psychiatric conditions. The researchers could only identify a numerical correlation between physical health diagnoses and mental health outcomes.

The database did not include a specific timeline of when each participant received their particular diagnoses. It remains entirely unclear whether the autoimmune disease developed before the emotional disorder, or the other way around. In some instances, a person might have experienced severe depression years before their immune system began attacking their joints or skin.

The study also depended entirely on self reported health histories. Without accessing actual medical records to confirm diagnoses, the findings remain subject to the accuracy of the participants’ memories. A definitive psychiatric diagnosis usually requires a structured clinical interview with a doctor, which was not feasible for a study involving over a million people.

Future investigations will need to track participants continuously over several years to determine the exact sequence of disease development. Tracking symptoms over time could reveal if surges in physical inflammation perfectly match the onset of low moods or an anxious state.

The authors hope eventually to incorporate direct biological measurements into large databases like Our Future Health. Analyzing actual blood samples for specific inflammatory proteins could help clarify if the severity of a person’s internal inflammation matches the severity of their mood symptoms. This level of detail would provide a much clearer picture of the biological mechanisms at play.

In a clinical setting, these widespread patterns suggest that medical professionals should consider implementing routine mental health screenings for patients dealing with autoimmune diseases. Catching symptoms of depression or anxiety early could help doctors provide tailored psychological support alongside standard physical treatments. Addressing both the immune system and emotional well being at the same time could improve the overall quality of life for millions of people.

The study, “Affective disorders and chronic inflammatory conditions: analysis of 1.5 million participants in Our Future Health,” was authored by Arish Mudra Rakshasa-Loots, Duncan Swiffen, Christina Steyn, Katie F M Marwick, and Daniel J Smith.