Bidirectional dual causality found between psoriasis and Crohn's disease in new study

A recent study, published in Scientific reports journal summarizes statistics from Mendelian Randomization (MR) analysis and says study strengthens the evidence for the bidirectional dual causality between psoriasis (including PsA) and Crohn's disease.

Yang Sun and team conducted a bidirectional analysis to evaluate the potential causal relationship between psoriasis, psoriatic arthritis (PsA), and inflammatory bowel disease (IBD).

Psoriasis is a most common skin disease, characterized by aberrant keratinocyte proliferation and immune cell infiltration into the epidermis. Approximately 2.5% of Europeans, 0.05–3% of Africans, and 0.1–0.5% of Asians are affected. Up to 30% of people with psoriasis is said to develop psoriatic arthritis (PsA), an inflammatory musculoskeletal condition.

The association between IBD and psoriasis, PsA, has recently gained much attention. Specifically, several observational studies have investigated a strong relationship between psoriasis, PsA, and IBD, involving genetics, immunity, and gut dysbiosis, whether this relationship is casual is uknown.

The current study used a two-sample bidirectional Mendelian randomization (MR) analysis to identify this relationship.

The key findings of the study are

• According to MR analysis, psoriasis and PsA causally increased the odds of developing Crohn's disease (OR = 1.350 (1.066–1.709) P = 0.013; OR = 1.319 (1.166–1.492) P < 0.001).

• In contrast, MR estimates gave little support to a possible causal effect of psoriasis, PsA, on ulcerative colitis (OR = 1.101 (0.905–1.340) P = 0.335; OR = 1.007 (0.941–1.078) P = 0.831).

• Similarly, the reverse analysis suggested the Crohn's disease causally increased the odds of psoriasis and PsA (OR = 1.425 (1.174–1.731) P < 0.001; OR = 1.448 (1.156–1.182) P = 0.001).

• There are no causal association between ulcerative colitis and psoriasis, PsA (OR = 1.192 (0.921–1.542) P = 0.182; OR = 1.166 (0.818–1.664) P = 0.396).

Yang Sun and team concluded that "In summary, our MR analysis strengthens the evidence for the bidirectional dual causality between psoriasis (including PsA) and Crohn's disease."

Reference: Sun, Y., Li, Y. & Zhang, J. The causal relationship between psoriasis, psoriatic arthritis, and inflammatory bowel diseases. Sci Rep 12, 20526 (2022). https://doi.org/10.1038/s41598-022-24872-5.