Bidirectional association between endometriosis, psoriasis, and psoriatic arthritis

From the Harris Group, Public Health Sciences Division

March is endometriosis awareness month. About 10% of reproductive age women are diagnosed with endometriosis, an estrogen-dependent inflammatory disorder in which endometrial-like tissue grows outside the uterus causing chronic pelvic pain, dysmenorrhea, and fertility issues. During the month of March with the aid of the Endometriosis Association, endometriosis awareness is promoted worldwide through activities such as education, fundraising, and marches. Because endometriosis is an immune-mediated disorder, it is known to be associated with several other immune-mediated disorders and possibly associated with psoriasis and psoriatic arthritis. Psoriasis, a skin disease characterized by red, itchy scaly patches.  Approximately 30% of people who have psoriasis are diagnosed with psoriatic arthritis (PsA) and experience its characteristic joint pain, stiffness, and swelling.  Previous literature suggests an association between psoriasis and endometriosis may exist, however, only one publication has examined the association. The Harris Group, from the Division of Public Health Sciences, was curious about the potential for shared underlying immunological and inflammatory dysfunction and sought to quantify the bidirectional association between endometriosis and psoriasis and PsA.  This paper is published in the American Journal of Epidemiology.

This study utilized data from the prospective Nurses’ Health Study II with over 22 years of follow-up.  A cohort of 87,860 participants were included in the analyses with psoriasis as the exposure and endometriosis as the outcome; in these analyses 4,112 cases of laparoscopically confirmed endometriosis were diagnosed over the study period.  An analytic sample of 91,380 participants were included in the analysis with endometriosis as the exposure and psoriasis as the outcome; there were a total of 697 incident cases of psoriasis.  Dr. Harris commented on the methods, “Because of the complexity of endometriosis, further impacted by diagnostic delays and the potential for ascertainment bias, we needed to utilize strong epidemiologic methods to examine these associations.” 

Psoriasis with PsA was associated with a 2-fold risk of endometriosis diagnosis, while psoriasis alone was not associated with endometriosis risk. In the second set of analyses, when endometriosis was defined as the exposure, it was not associated with psoriasis without PsA, but was suggestively associated with psoriasis with PsA.  PsA typically occurs at least 8-10 years after an onset of psoriasis thus PsA may represent a phase of disease progression with higher inflammatory burden.

This study uniquely examined a prospective association between inflammation related conditions. Dr. Harris elaborated, “This is the first study to examine the bi-directional association between psoriasis, psoriatic arthritis, and endometriosis. These are important findings as early diagnosis and treatment of the index condition, both endometriosis and psoriatic arthritis, may help to minimize the emergence of subsequent comorbidities, ultimately improve the quality of life of patients.” Dr. Harris concluded, “The mechanisms underlying the endometriosis-psoriatic arthritis association remain to be elucidated, but there are hints regarding inflammatory and genetic pathways within the small existing literature. Future studies are needed to explore whether specific phenotypes of endometriosis are more strongly associated with psoriatic arthritis and whether any treatments for psoriatic arthritis increase or decrease the likelihood of endometriosis diagnosis.“


This research was supported by the Eunice Kennedy Shriver National Institute of Child Health and Human Development.

Fred Hutch/UW Cancer Consortium member Holly R. Harris contributed to this work.

Harris HR, Korkes KM, Li T, Kvaskoff M, Cho E, Carvalho LF, Qureshi AA, Abrao M, Missmer SA. 2022. Endometriosis, psoriasis and psoriatic arthritis: A prospective cohort study. Am. J. Epidemiol. Online ahead of print.