Irritable bowel syndrome linked to increased risk of psoriasis: 14-year study of more than 437,000 people

Irritable bowel syndrome is generally considered a disorder of the gut-brain interaction: people experience abdominal pain and bowel irregularities, although no structural disorder can be identified that fully explains the symptoms. However, a growing body of research suggests that the consequences of this condition may extend beyond the gastrointestinal tract. A large new study points to another potential link – with the chronic inflammatory skin condition psoriasis.

Beijing-based scientists analyzed data from 437,170 UK Biobank participants who were psoriasis-free at baseline. Of these, 21,748, or approximately 5% of the entire sample, had been diagnosed with irritable bowel syndrome at study entry. The median follow-up period was 14.4 years, allowing them to assess the long-term likelihood of a new psoriasis diagnosis.

During the observation period, psoriasis was newly diagnosed in 4,325 participants. After accounting for age, gender, body weight, smoking, alcohol consumption, physical activity level, socioeconomic status, type 2 diabetes, anti-inflammatory drug use, and C-reactive protein levels, the presence of irritable bowel syndrome was associated with a 35% increased relative risk of developing psoriasis. The adjusted odds ratio was 1.35, with a 95% confidence interval of 1.19 to 1.52.

However, the study does not prove that irritable bowel syndrome directly causes psoriasis. The absolute difference between the groups was relatively small: the cumulative incidence of psoriasis was approximately 0.88% among people with irritable bowel syndrome versus 0.69% among the other participants. The authors specifically emphasize that the statistically significant increase in relative risk should not be interpreted as a high probability of psoriasis in every patient with intestinal symptoms.

Research in numbers

Indicator	Result
UK Biobank initial cohort	502,411 people
Final analytical sample	437,170 people
Middle age	56.2 years
Women	53.3%
Participants with irritable bowel syndrome	21,748 (5.0%)
Median observation	14.4 years
New cases of psoriasis	4325
Psoriasis among the group with irritable bowel syndrome	292 cases
Psoriasis among other participants	4033 cases
Adjusted hazard ratio	1.35
95% confidence interval	1.19-1.52

Source: Study by Qiu et al. in the Journal of Global Health.[1]

How scientists tested the link between the gut and psoriasis

For their analysis, the researchers used the UK Biobank, a large British population-based cohort that included people aged 37 to 73 years from 2006 to 2010. Participants completed questionnaires, underwent physical and laboratory examinations, and their data were subsequently linked to medical records. Follow-up in the new study continued until the first diagnosis of psoriasis, death, loss of contact with the participant, or September 30, 2023.

Of the initial 502,411 participants, the authors excluded people with pre-existing psoriasis, as well as patients with certain conditions that could significantly complicate the interpretation of the relationship between the gut and skin inflammation. Specifically, participants with inflammatory bowel disease, celiac disease, systemic lupus erythematosus, and cancer were excluded. After applying the selection criteria, 437,170 people remained.

Irritable bowel syndrome was defined using the International Classification of Diseases, Tenth Revision code K58. Self-reports, primary care records, and hospitalization data were used. Psoriasis during follow-up was similarly defined using the code L40. All individuals with pre-existing psoriasis at the start of the study were excluded, so the researchers analyzed only new cases.

Cox proportional hazards models were used for statistical evaluation. The authors gradually added potential confounding factors: first, age and gender, then ethnicity, education, socioeconomic status, body mass index, alcohol, smoking, and physical activity. In the most comprehensive model, they also accounted for type 2 diabetes, nonsteroidal anti-inflammatory drug use, and C-reactive protein levels. Even after these adjustments, the association persisted.

What factors were taken into account in the analysis?

Factor	Why take it into account?
Age	The risk of psoriasis and other diseases changes with age.
Floor	The prevalence of irritable bowel syndrome differs between men and women.
Body mass index	Obesity linked to chronic inflammation and psoriasis
Smoking	May affect inflammatory processes
Alcohol	Potentially linked to risk of psoriasis
Physical activity	Linked to metabolic and inflammatory health
Socioeconomic situation	May reflect differences in lifestyle and access to healthcare
Type 2 diabetes mellitus	Associated with metabolic disorders
C-reactive protein	Marker of systemic inflammation
Anti-inflammatory drugs	May potentially influence inflammation and disease detection

[2]

Psoriasis was more common, but the absolute difference remained small

Over more than six million person-years of follow-up, researchers recorded 4,325 new cases of psoriasis. Among 21,748 participants with irritable bowel syndrome, the disease developed in 292. In the group without baseline irritable bowel syndrome, psoriasis was recorded in 4,033 of 415,422 participants.

The cumulative incidence rate during the observation period was 0.88% in the irritable bowel syndrome group and 0.69% in the control group. The difference in absolute values is approximately 0.19 percentage points. In other words, the study reveals a statistically significant difference between very large groups, but this does not mean that psoriasis is a typical or inevitable complication of irritable bowel syndrome.

In the unadjusted analysis, the odds ratio was 1.35. After adjusting for age and gender, the ratio increased to 1.41, and after adding a large number of other factors, it returned to 1.35. The stability of the estimate with successive increases in the complexity of the statistical model suggests that the observed association is not explained solely by differences in age, body weight, smoking, or other characteristics included in the model.

However, it's crucial to distinguish between the concepts of relative and absolute risk. "A 35% higher risk" means that the ratio of incidence between the two groups over time was approximately 1.35. This doesn't mean that 35% of people with irritable bowel syndrome will develop psoriasis. In fact, the absolute incidence in the study remained below one percent in both groups. The authors themselves note the small absolute difference and recommend caution in assessing the public health significance of this finding.

What is the difference between relative and absolute risk?

Indicator	With irritable bowel syndrome	Without syndrome
Number of participants	21,748	415 422
New cases of psoriasis	292	4033
Cumulative incidence of psoriasis	0.88%	0.69%
Absolute difference	≈0.19 percentage points	-
Adjusted hazard ratio	1.35	1.00
Relative increase in risk	≈35%	-

Thus, the result is statistically significant, but the absolute additional risk is small. [3]

The connection was maintained through multiple additional checks.

One of the strengths of the study was the large number of sensitivity analyses. The researchers attempted to verify whether the association would disappear if they changed the statistical analysis rules or excluded certain categories of participants. In almost all cases, the result remained close to the original one: the increased risk of psoriasis in people with irritable bowel syndrome persisted.

For example, the authors excluded cases of psoriasis diagnosed within the first year of follow-up. This reduced the likelihood of so-called reverse causality—a situation in which latent or incipient psoriasis could have somehow affected the patient's condition before the official diagnosis. The odds ratio remained virtually unchanged: 1.35. Even after excluding the first two years of follow-up, the result remained the same.

After excluding all users of nonsteroidal anti-inflammatory drugs, the odds ratio was 1.40. Using a statistical model that considered death and loss to follow-up as competing events, the odds ratio was 1.38. After additional adjustment for the polygenic risk of psoriasis, the odds ratio was 1.35, and after accounting for dietary factors, it was also approximately 1.35.

An interesting result emerged after additional adjustment for anxiety and depressive disorders. The association became somewhat weaker but still remained statistically significant: the odds ratio was 1.26. This demonstrates that psychological and psychiatric factors may indeed explain some of the overall association, but they do not eliminate it entirely.

How robust was the main result?

Additional analysis	Odds ratio for psoriasis
The main fully adjusted model	1.35 (1.19-1.52)
Cases in the first year were excluded	1.35 (1.19-1.53)
Cases in the first two years are excluded	1.35 (1.19-1.53)
Users of anti-inflammatory drugs are excluded	1.40 (1.18-1.68)
Competing events are statistically taken into account	1.38 (1.22-1.55)
Additional adjustment for anxiety and depression	1.26 (1.11-1.43)
Adjustment for genetic risk of psoriasis	1.35 (1.19-1.53)
Nutritional adjustment	1.35 (1.19-1.52)
Self-reports of psoriasis were excluded.	1.37 (1.21-1.55)
Multiple imputation of missing data	1.36 (1.20-1.53)

[4]

The risk was increased even in people with a low genetic predisposition.

The authors further divided the participants into subgroups based on age, gender, smoking status, systemic inflammation levels, anti-inflammatory drug use, socioeconomic status, and genetic predisposition to psoriasis. In most of these groups, the association between irritable bowel syndrome and subsequent psoriasis remained unidirectional, with a higher risk.

It is particularly interesting that the relative association was more pronounced in participants with a low polygenic risk for psoriasis. The authors suggest that with a high hereditary predisposition, the contribution of genetics is so significant that the additional influence of irritable bowel syndrome becomes relatively less noticeable. In contrast, in individuals with a low genetic risk, the influence of other factors may be easier to detect statistically.

A similar pattern was observed for anxiety and depression: the link between irritable bowel syndrome and psoriasis was stronger among people without these conditions. Researchers propose a similar explanation: the strong influence of psychoemotional factors may partially "mask" the relative contribution of intestinal disease. However, this is still a hypothesis, not a proven biological mechanism.

Interesting data were also obtained when analyzing the duration of irritable bowel syndrome. If irritable bowel syndrome had been present for no more than ten years, the odds ratio for subsequent psoriasis was 1.45. For a disease duration of more than ten years, the ratio was 1.26. The authors suggest that immune regulation or intestinal barrier dysfunction may be more pronounced in the early stages of irritable bowel syndrome, but specific mechanistic studies are needed to confirm this hypothesis.

Duration of irritable bowel syndrome and risk of psoriasis

State	Odds ratio for psoriasis	95% confidence interval
No irritable bowel syndrome	1.00	Reference
Duration of the syndrome ≤10 years	1.45	1.22-1.71
Duration of the syndrome >10 years	1.26	1.06-1.51

Both categories were statistically associated with an increased risk compared with people without irritable bowel syndrome.[5]

How the gut could theoretically be linked to skin disease

The authors consider several possible biological mechanisms. The first is chronic, low-intensity systemic inflammation. Irritable bowel syndrome was long considered a primarily functional disorder, but it is now known that some patients exhibit altered immune regulation and inflammatory signaling. The researchers point in particular to mediators such as tumor necrosis factor-alpha and interleukin-23, which are also involved in inflammatory responses in psoriasis.

The second possible link between the two diseases involves cellular immunity. In irritable bowel syndrome, impaired T-lymphocyte activation and altered responses of T-helper cells type 1 and 17 have been described. Similar immunological pathways are also important in psoriasis, where dysregulation of T-cells and their associated cytokines is a central element of pathogenesis.

The third hypothesis concerns the gut microbiota and the gut-skin axis. Altered gut microbiota composition could potentially influence intestinal barrier permeability. If microbial components more easily enter the systemic circulation, the immune system receives additional inflammatory signals. Theoretically, this process could affect not only the gut but also distant organs, including the skin. For now, this is a biologically plausible model, not a proven sequence of events in the participants of this study.

Finally, the authors draw attention to stress. Irritable bowel syndrome is often accompanied by anxiety, emotional tension, and other psychoemotional disorders. Chronic stress can alter the functioning of the hypothalamic-pituitary-adrenal axis and neuroimmune regulation, and stressful events have long been considered a factor that can exacerbate psoriasis symptoms in predisposed individuals.

Possible links in the gut-skin axis

Possible mechanism	What could be happening?	How is this potentially related to psoriasis?
Systemic inflammation	Increased activity of inflammatory mediators	May support skin inflammation
T-cell dysregulation	Altered immune cell function	Similar pathways are involved in psoriasis
Dysbiosis of intestinal microbiota	The composition of microorganisms changes	May alter systemic immune response
Disruption of the intestinal barrier	The permeability of the mucous membrane increases	Microbial components may enhance immune activation
Gut-skin axis	Changes in the intestinal environment affect other tissues	Potentially alters the immune homeostasis of the skin
Psychological stress	Hormonal and neuroimmune mechanisms are activated	May promote inflammatory reactions

These mechanisms are proposed by the authors as explanations and are not directly proven by this cohort study. [6]

Irritable bowel syndrome has been linked to more than just intestinal symptoms.

The study's findings fit into a broader concept that irritable bowel syndrome cannot be viewed solely as a localized gastrointestinal motility disorder. The authors note that this disorder is increasingly associated with low-grade systemic inflammation, metabolic and immune comorbidities, as well as anxiety and depression.

Psoriasis, in turn, has long ceased to be perceived solely as a skin condition. It is a chronic immune-mediated inflammatory disorder that can be accompanied by metabolic, cardiovascular, and gastrointestinal disturbances. Therefore, the discovery of an epidemiological link between the two conditions appears biologically plausible, although it alone does not yet indicate the direction of causality.

Previous cross-sectional and case-control studies have shown that irritable bowel syndrome and psoriasis co-occur more frequently than expected by chance. However, these studies could not reliably determine which condition developed first. The new study significantly strengthens the evidence base precisely because the participants were psoriasis-free at baseline and were then followed for a median of 14.4 years. According to the authors, this is the first large prospective cohort study specifically examining the risk of new-onset psoriasis in patients with irritable bowel syndrome.

But even such a design doesn't prove causality. It's possible to show that one condition statistically precedes another, but it's impossible to completely rule out shared genetic, immune, drug, dietary, or behavioral factors. Therefore, the result is more accurately stated as follows: people with irritable bowel syndrome in this British cohort were subsequently diagnosed with psoriasis more often, rather than "irritable bowel syndrome causes psoriasis."

Should all patients with irritable bowel syndrome now be tested for psoriasis?

The authors believe the findings support greater vigilance for skin manifestations in patients with irritable bowel syndrome. However, this does not necessitate complex laboratory or instrumental screening. Psoriasis typically presents with noticeable, persistent skin lesions, and suspicious symptoms are diagnosed clinically by a dermatologist.

From a practical standpoint, the study suggests that physicians should not automatically dismiss skin complaints in patients with irritable bowel syndrome as unrelated to the overall disease. The appearance of persistent, red, flaky patches, especially on the scalp, elbows, knees, and other typical areas, may warrant evaluation by a dermatologist. However, the presence of irritable bowel syndrome alone does not constitute a diagnosis of psoriasis and does not necessarily mean the patient will develop it.

This is especially important given the small absolute risk difference. Over the long-term observation period, psoriasis developed in approximately 0.88% of people with irritable bowel syndrome versus 0.69% of people without it. Therefore, mass screening of all asymptomatic patients can hardly be justified by these data alone. The authors suggest, rather, the possibility of more individualized monitoring and early consultation with a dermatologist in people who develop relevant symptoms.

The next important question is whether the risk of psoriasis can be reduced by targeting the gut. The answer remains unclear. Researchers suggest future studies testing whether interventions targeting the microbiota, gut health, systemic inflammation, or psychological stress can alter the likelihood of developing psoriasis. This will require interventional studies, as the current analysis did not examine the effectiveness of probiotics, diet, or irritable bowel syndrome treatment in preventing the skin condition.

What the study means—and what it doesn't mean

It can be concluded	It is impossible to conclude
Irritable bowel syndrome linked to increased long-term risk of psoriasis	Irritable bowel syndrome has been proven to cause psoriasis.
The association survived numerous amendments.	All patients with irritable bowel syndrome will develop psoriasis.
Common immune and microbiotic mechanisms are possible	Microbiota has already been proven to be the cause of the identified connection
Skin symptoms in such patients deserve attention.	All patients need preventative treatment for psoriasis.
Further mechanistic studies are needed.	Dietary changes or taking probiotics have been shown to prevent psoriasis.

[7]

Why the result should be interpreted with caution

The study's main strength is its scale. More than 437,000 participants and a median follow-up of 14.4 years allow for the detection of even relatively small differences in disease risk. Furthermore, the authors conducted numerous sensitivity analyses and obtained similar results under different statistical assumptions, reducing the likelihood that the main finding is a random feature of a single model.

However, the study is based on observational data. Scientists were not able to randomly assign participants to irritable bowel syndrome, so differences between the comparison groups are inevitable. For example, there were significantly more women among patients with irritable bowel syndrome—73.2% versus 52.3% in the control group—and significantly more anxiety and depressive disorders. Statistical adjustment reduces the influence of such factors, but does not guarantee complete elimination of confounding.

There's also the issue of diagnostic overrepresentation. People with irritable bowel syndrome may visit doctors more frequently, meaning they are potentially more likely to be diagnosed with psoriasis. The authors attempted to test this effect by excluding conditions diagnosed shortly after the start of the study, and the primary result remained unchanged. However, it's impossible to completely eliminate this type of bias in an observational study.

Furthermore, the researchers lacked information on the subtypes and severity of irritable bowel syndrome. They were unable to fully account for the use of antibiotics, corticosteroids, and probiotics. Finally, the vast majority of participants were white—approximately 94% of the entire sample—so it is unknown whether the association would be replicated to the same extent in other ethnic and geographic populations.

Strengths and Limitations

Strengths	Restrictions
437,170 participants	Observational rather than randomized design
14.4 years median follow-up	It is impossible to definitively prove causality
Excluding people with psoriasis at the start	Diagnostic suspicion may be increased in patients with irritable bowel syndrome.
Multivariate statistical adjustment	Not all medications and lifestyle factors were available
Genetic risk testing	There was no information on the severity of irritable bowel syndrome.
Multiple sensitivity analyses	Individual subtypes of the syndrome were not analyzed.
Only new cases of psoriasis	About 94% of participants are white.

[8]

What's changing in the concept of the gut-skin axis?

The study's primary scientific interest lies not so much in the additional 0.19 percentage points of absolute risk, but in confirming the idea of a biological connection between organs previously considered virtually independently. Disturbances in intestinal function can potentially impact immune processes far beyond the digestive system. The skin, with its own complex immune system, may be one such target organ.

If further research confirms the causal component of this association, the question arises about the possibility of simultaneously targeting multiple elements of the pathological chain. Theoretically, the intestinal microbiota, mucosal permeability, systemic inflammation, stress, and other factors could be studied. However, at present, these are primarily areas for future research rather than proven methods for preventing psoriasis.

The polygenic risk results are no less important. A stronger association in people with a relatively low genetic predisposition reminds us that chronic inflammatory diseases cannot be explained by heredity alone. Genetics may provide a background, but the interaction of the immune system, environment, gut microbes, stress, and other factors potentially determines whether the disease will manifest clinically. It is these interactions that the authors propose further study.

Ultimately, the new study doesn't turn irritable bowel syndrome into a "precursor to psoriasis." It reveals a more cautious and scientifically interesting pattern: in a large British cohort, people with pre-existing irritable bowel syndrome were slightly more likely to be diagnosed with psoriasis over the subsequent 14 years, a difference that persisted after accounting for a number of potentially influencing factors. The next step is to determine whether this association reflects a common inflammatory mechanism, the gut-skin axis, or a combination of several processes.

Key figures of the study

Indicator	Meaning
Participants	437 170
With irritable bowel syndrome	21,748
Without syndrome	415 422
Middle age	56.2 years
Median observation	14.4 years
Total number of new cases of psoriasis	4325
Cases in the irritable bowel syndrome group	292
Cumulative incidence of psoriasis in the syndrome	0.88%
Cumulative frequency without syndrome	0.69%
Adjusted hazard ratio	1.35
Relative increase in risk	35%
Risk with a duration of the syndrome of ≤10 years	1.45
Risk with duration of syndrome >10 years	1.26

[9]

News source

Qiu Y, Zhou Y, Liu S, Zhang Q, Zhang S, Wu J, Zhu S, Wu S. Long-term risk of incident psoriasis in patients with irritable bowel syndrome: a large-scale prospective cohort study. Journal of Global Health. 2026;16:04140. The article was published on August 7, 2026.

DOI: 10.7189/jogh.16.04140.

The study was funded by the National Natural Science Foundation of China and the Beijing Nova Program. The authors declare no relevant conflicts of interest; data were obtained from UK Biobank under application no. 74444.