Background:
Previous investigations have demonstrated a high rate of depression in patients with severe tinnitus. In most studies, sum scores have been used for diagnosing depression, and it remains debated whether these scores reflect a comorbid depressive disorder or rather distress caused by tinnitus.

Methods:
To determine whether this elevated rate may partly result from symptom overlap between severe tinnitus and depression, the Major Depression Inventory (MDI) was administered to a cohort of 2693 patients with chronic tinnitus. Data were evaluated both categorically according to ICD-10 diagnostic criteria and dimensionally using total sum scores.

Results:
The categorical approach indicated a rate of 17.1%, whereas the dimensional assessment yielded a rate of 28.5%. To examine whether this discrepancy was specific to tinnitus or represented a methodological limitation of the MDI, a comparable analysis was conducted in patients with clinically diagnosed depression. This analysis also revealed a higher rate (86.4% vs. 69.7%) and greater severity under the dimensional framework. After lowering the threshold for core symptoms in the categorical approach, the rate estimates across evaluation systems aligned (Depression: 86.4% vs. 83.3%; Tinnitus: 28.5% vs. 27.3%).

Conclusion:
Core depressive symptoms frequently occur in tinnitus but appear to show greater temporal variability than in major depression. Differences in rates arise from both symptom overlap and methodological factors. Self-report scales have limitations, particularly with somatic or psychiatric comorbidity. Future studies should incorporate observer-rated scales or diagnostic interviews. Clinically, distinguishing depressive symptoms related to severe tinnitus from coexisting depression remains challenging.