ImportancePatients with hidradenitis suppurativa (HS) have an increased risk of new-onset depression and anxiety, but whether disease severity is a potential independent risk factor remains unknown.ObjectiveTo assess the risk of new-onset and recurrent depression and anxiety among patients with HS and its association with disease severity compared with the background population.Design, Setting, and ParticipantsThis population-based cohort study from 1997 to 2022 included Danish patients with HS who were age and sex matched 1:4 with individuals without HS from the Danish national registries. Data were analyzed from July 18, 2024 to May 20, 2025.ExposureHospital-diagnosed HS.Main Outcomes and MeasuresThe main outcomes were first diagnosis of depression or anxiety, as well as first diagnosis of depression and anxiety as separate outcomes after index date. Incidence rates (IRs) and hazard ratios (HRs) were calculated for the first episode of anxiety or depression after baseline using Cox regression models adjusted for demographic and socioeconomic factors as well as comorbidities. Disease severity was defined as treatments received (topicals, systemic nonbiologics, or biologics) and hospitalizations for HS-related surgical procedures (0, 1, 2, or ≥3).ResultsA total of 10 206 patients with HS and 40 125 controls were included (mean [SD] age, 38.0 [13.6] years; 69.9% female in both groups). Throughout the study period, 12.0% received topical only, 55.5% systemic nonbiologic, 6.5% biologic, and 25.9% no HS-related treatments. The adjusted HRs were 1.69 (95% CI, 1.57-1.81; P &lt; .001) for new-onset depression and 1.48 (95% CI, 1.38-1.56; P &lt; .001) for new-onset anxiety. Stratified by treatment, the HRs for either depression or anxiety were 1.62 (95% CI, 1.41-1.85; P &lt; .001) for topicals, 1.61 (95% CI, 1.51-1.72; P &lt; .001) for systemic nonbiologics, and 1.38 (95% CI, 1.01-1.87; P &lt; .05) for biologics. By 0, 1, 2, or 3 or more hospitalizations for HS-related surgical procedures, the HRs were 1.44 (95% CI, 1.36-1.53; P &lt; .001), 1.66 (95% CI, 1.53-2.17), 1.59 (95% CI, 1.33-1.90; P &lt; .001), and 1.60 (95% CI, 1.40-1.85; P &lt; .001), respectively. More patients with HS had a history of depression (7.0% vs 0.3%; P &lt; .001) and anxiety (5.9% vs 0.5%; P &lt; .001) than controls; however, no difference in the risk of recurrent depression (HR, 0.90 [95% CI, 0.62-1.28]; P = .55) or anxiety (HR, 1.22 [95% CI, 0.89-1.66]; P = .22) was observed.Conclusion and RelevanceThese findings suggest that patients with HS had an elevated risk of new-onset depression and anxiety. Using treatment- and HS-related surgical procedures as severity markers, no consistent differences in mental health risk across severity levels were observed, emphasizing the need for psychiatric assessment and intervention across all patients with HS regardless of disease severity.