Psychiatric and systemic comorbidity burden in hidradenitis suppurativa: a nationwide Danish comparison with psoriasis and the general population

Background: Hidradenitis suppurativa (HS) is a chronic inflammatory skin disease increasingly recognised as a systemic disorder with substantial psychiatric morbidity. While psychiatric comorbidity is reported in HS, most evidence has focused on depression and anxiety, leaving unclear whether its broader psychiatric profile reflects the pronounced systemic and immune-inflammatory involvement of the disease and may inform biological models of psychiatric comorbidity.

Aim: This study aimed to characterise the psychiatric comorbidity profile of HS and examine its co-occurrence with metabolic, cardiovascular, neurological, and immune-mediated diseases, using matched psoriasis and general population comparators.

Methods: We conducted a nationwide registry-based retrospective cohort study using Danish health and psychiatric registers from 1977 to 2016. Individuals with International Classification of Diseases-coded HS were identified and matched 1:1 with psoriasis controls by birth month and year, sex, and registry follow-up. General population controls were matched 1:10 by exact birth date and sex across 50 bootstrapped control sets to improve estimate stability. Lifetime registry-based psychiatric and systemic diagnoses were assessed. Categorical variables were compared using chi-square tests. Odds ratios (ORs) with 95% confidence intervals (CIs) were calculated, with Bonferroni correction applied within diagnostic categories.

Results: The study included 12,438 individuals with HS; 70.5% were female and 29.5% male, with a mean age at diagnosis of 36.9 years. Depressive disorders were present in 1,313 individuals with HS (10.6%), and anxiety disorders in 729 individuals (5.9%). Compared with psoriasis controls, HS was associated with higher odds of depressive disorders (OR = 1.25, 95% CI 1.15-1.36), anxiety disorders (OR = 1.33, 95% CI 1.19-1.49), psychotic disorders (OR = 1.34, 95% CI 1.17-1.53), schizophrenia (OR = 1.37, 95% CI 1.15-1.62), and ADHD (OR = 1.67, 95% CI 1.29-2.16). Compared with general population controls, HS showed higher odds of ADHD (OR = 3.29, 95% CI 2.74-3.94), schizophrenia (OR = 2.83, 95% CI 2.49-3.21), psychotic disorders (OR = 2.55, 95% CI 2.31-2.81), depressive disorders (OR = 2.50, 95% CI 2.35-2.66), anxiety disorders (OR = 2.40, 95% CI 2.21-2.61), and OCD (OR = 2.05, 95% CI 1.61-2.60). Within the HS cohort, individuals with psychiatric diagnoses had higher odds of migraine (OR = 2.10, 95% CI 1.69-2.63), Parkinson’s disease (OR = 3.28, 95% CI 2.15-5.01), type 2 diabetes (OR = 1.60, 95% CI 1.40-1.83), obesity (OR = 1.64, 95% CI 1.48-1.83), hypertensive diseases (OR = 1.41, 95% CI 1.26-1.58), and ischaemic heart disease (OR = 1.27, 95% CI 1.10-1.47).

Conclusions: HS was associated with a broad psychiatric comorbidity profile and increased systemic disease burden, underscoring the potential value of integrated dermatological, psychiatric, and cardiometabolic assessment. The findings suggest that HS may provide a clinically informative model for studying immune-inflammatory contributions to psychiatric comorbidity. However, the observational registry-based design precludes causal inference, and longitudinal mechanistic studies are needed to clarify temporal pathways.

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