Patients with Hidradenitis Suppurativa Have a High Psychiatric Disease Burden: A Finnish Nationwide Registry Study.

Hidradenitis suppurativa (HS) is a chronic inflammatory skin disease of hair follicles that is associated with various comorbidities. To further clarify the associations between HS and psychiatric disorders, we conducted a nationwide retrospective study that included 4,381 patients with HS, and 39,554 with psoriasis and 43,248 with melanocytic nevi as controls. Patient data were obtained from the statutory Finnish Care Register for Health Care. The incidence of HS was 3.0/100,000 persons/year. At least one psychiatric diagnosis was found in 24.1% of the patients with HS compared with 19.1% of the patients with psoriasis (odds ratio 1.34; 95% confidence interval 1.24-1.46) and 13.5% of those with melanocytic nevi (odds ratio 2.04; confidence interval 1.88-2.22). Every mental disorder examined was significantly more frequent in HS than in the two other groups. Mental disorders were more common in women than in men with HS and psoriasis. The main finding of our study is that patients with HS have a higher risk of mental disorders than patients with psoriasis. Additionally, this study reveals that HS is associated with both schizophrenia (odds ratio 1.57; confidence interval 1.24-1.98) and bipolar disorder (odds ratio 1.81; confidence interval 1.47-2.23), findings that to our knowledge have not been reported previously.