| Author | Year | Location | Study type | Population | Number of IBD | Psoriasis patients | Newcastle- Ottawa score |
| Hammer et al. [18] | 1968 | England | Case-control | NA | 243 | 5 | 5 |
| Yates et al. [19] | 1982 | England | Case-control | Mixed | 204 | 18 | 5 |
| Lakatos et al. [20] | 2003 | Hungary | Cohort | Mixed | 873 | 4 | 7 |
| Bernstein et al. [21] | 2005 | Canada | Cohort | Mixed | 8060 | 749 | 6 |
| Weng et al. [22] | 2007 | USA | Cross-sectional | Mixed | 12,601 | 242 | 5 |
| Bardella et al. [23] | 2008 | Italy | Cross-sectional | Mixed | 180 | 3 | 6 |
| Yüksel et al. [24] | 2009 | Turkey | Cohort | Mixed | 352 | 11 | 5 |
| Ciccacci et al. [25] | 2013 | Italy | Cohort | NA | 467 | 21 | 7 |
| Vavricka et al. [26] | 2015 | Switzerland | Cohort | Mixed | 1249 | 10 | 8 |
| Singh et al. [27] | 2015 | India | Cohort | Mixed | 1652 | 7 | 6 |
| Lolli et al. [28] | 2015 | Italy | Case-control | Mixed | 251 | 62 | 8 |
| Card et al. [29] | 2016 | England | Cohort | Mixed | 56,097 | 2856 | 7 |
| Kim et al. [30] | 2016 | Korea | Cross-sectional | Mixed | 40,843 | 636 | 6 |
| Karmiris et al. [31] | 2016 | Greece | Cohort | Adult | 1860 | 51 | 7 |
| Halling et al. [32] | 2017 | Denmark | Cross-sectional | Mixed | 47,325 | 378 | 5 |
| Vide et al. [33] | 2018 | Portugal | Cohort | Mixed | 342 | 24 | 7 |
| Napolitano et al. [34] | 2019 | Italy | Cohort | NA | 200 | 32 | 5 |
| Yehuda et al. [35] | 2019 | Israel | Cohort | Mixed | 12,625 | 614 | 7 |
| Ghersin et al. [36] | 2020 | Israel | Cohort | Adolescents | 2372 | 36 | 5 |
| Edigin et al. [37] | 2021 | USA | Cross-sectional | Mixed | 184,120 | 2255 | 7 |
| Koumaki et al. [38] | 2021 | Greece | Cohort | Mixed | 806 | 30 | 7 |
| JO et al. [39] | 2021 | Korea | Cross-sectional | Mixed | 64,837 | 929 | 6 |
| Tillack et al. [40] | 2014 | Germany | Cohort | Adult | 434 | 21 | 6 |
| George et al. [41] | 2015 | USA | Cohort | Mixed | 521 | 18 | 6 |
| Fréling et al. [42] | 2015 | France | Cohort | Adult | 583 | 59 | 6 |
| Pugliese et al. [43] | 2015 | England | Cohort | NA | 1384 | 33 | 7 |
| Guerra et al. [44] | 2016 | Spain | Case-control | Mixed | 7415 | 125 | 7 |
| Protic et al. [45] | 2016 | Switzerland | Cohort | NA | 752 | 34 | 7 |
| Peer et al. [46] | 2017 | Australia | Cohort | Adult | 270 | 10 | 6 |
| Sridhar et al. [47] | 2018 | USA | Cohort | Children | 409 | 33 | 7 |
| Weizman et al. [48] | 2018 | Canada | Cohort | NA | 676 | 72 | 7 |
| Andrad et al. [49] | 2018 | Portugal | Cohort | Mixed | 732 | 39 | 6 |
| Courbette et al. [50] | 2019 | France | Cohort | Children | 147 | 20 | 5 |
| Buckley et al. [51] | 2021 | USA | Cohort | Children | 3035 | 50 | 6 |