TNF and rheumatoid arthritis: In summary, we arrived at three sets of conclusions: (i) all TNF inhibitors have a statistically significant association with psoriasis in RA treated patients compared to the single methotrexate control group, (ii) not all of the non-TNF inhibitor treatments were associated with psoriasis compared to the single methotrexate control group, with some overlapping with the TNF inhibitor 95% CI ranges, (iii) pairwise comparisons of certolizumab pegol with both other TNF inhibitors and non-TNF inhibitor therapeutics show a greater and statistically significant association with psoriasis.