Tinnitus refers to the conscious perception of sound without an external source, while tinnitus disorder denotes tinnitus accompanied by emotional, cognitive or functional impairment. Psychological factors, notably symptoms of depression, are frequently associated with the degree of tinnitus-related distress. Because both constructs are commonly measured with self-report questionnaires, overlap in item content may inflate observed associations or complicate interpretation. To systematically characterize this overlap, the authors applied the International Classification of Functioning, Disability and Health (ICF) as a standardized content-mapping framework.
The content analysis included six validated, multi-item self-report measures of tinnitus distress: Tinnitus Handicap Inventory (THI), Tinnitus Questionnaire (TQ), mini Tinnitus Questionnaire (mTQ), Tinnitus Handicap Questionnaire (THQ), Tinnitus Reaction Questionnaire (TRQ), and Tinnitus Functional Index (TFI). Also analyzed were seven validated depressive symptom questionnaires: Beck Depression Inventory-II (BDI-II), Hospital Anxiety and Depression Scale depression subscale (HADS-D), Zung Self-Rating Depression Scale (SDS), Patient Health Questionnaire-9 (PHQ-9), Center for Epidemiologic Studies Depression Scale (CES-D), Symptom Checklist-90-Revised depression subscale (SCL-90-R), and Depression Anxiety Stress Scale depression subscale (DASS-42).
Items from each questionnaire were mapped to the most specific ICF categories following established linking rules by Cieza et al. The ICF structure used distinguishes functioning and disability (body functions & structures; activities & participation) and contextual factors (environmental and personal factors). When an item contained multiple concepts, more than one ICF category could be assigned. Concepts not represented in the ICF were coded as nc (not covered), personal factors as pf, and insufficiently defined items as nd (not definable).
Two independent reviewers (a psychologist and a biomedical researcher) performed initial linking for all items. Discrepancies and ambiguous mappings were resolved iteratively through discussion. A third reviewer (an ENT specialist and epidemiologist) adjudicated remaining disagreements and helped establish consistent coding rules across conceptually similar items. Several specific coding decisions were made and applied consistently across instruments.
A deliberate decision treated items that explicitly named tinnitus as the direct object (for example, "ability to ignore your tinnitus") as inseparable from the tinnitus experience and linked them to hearing and vestibular functions (b240), more specifically to tinnitus (b2400). The authors note an alternative interpretation is possible—these items might reflect more general processes (e.g., coping) manifested in relation to tinnitus. To assess the impact of this interpretive choice, an alternative coding strategy recoded such items to broader ICF categories where plausible; items clearly describing the percept (loudness, presence) remained under b240.
Analyses were performed at the ICF second-level category. The frequency and percentage of assigned second-level codes were reported per questionnaire and for the combined tinnitus and depressive questionnaire sets. Overlap between the two groups was determined by the presence of shared second-level ICF categories and by calculating instrument-level overlap ranges at that second-level granularity.
At the second-level ICF categorization, the combined depressive symptom questionnaires covered 14 ICF categories, whereas the combined tinnitus distress questionnaires covered 23 categories, indicating broader domain coverage among the tinnitus measures. Seven second-level ICF categories were shared between tinnitus distress and depressive symptom questionnaires: energy and drive functions, sleep functions, attention functions, emotional functions, thought functions, interpersonal interactions and relationships, and recreation and leisure.
Overlap with depressive symptom questionnaires varied markedly across tinnitus measures. At the second-level ICF category:
Among the depressive symptom instruments:
These ranges reflect the proportion of second-level ICF categories assigned to one instrument that were also present in the other instrument set.
The documented overlap between tinnitus distress and depressive symptom questionnaires underscores the need for careful instrument selection and cautious interpretation of scores when assessing comorbid tinnitus-related distress and depressive symptoms. Overlap in questionnaire content may inflate associations in observational studies, influence participant selection in clinical trials, and affect treatment decision-making when instruments do not cleanly separate tinnitus-specific impact from depressive symptomatology. The results can guide clinicians and researchers in choosing measures aligned with their goals—for example, selecting instruments with less overlap when the aim is to distinguish depressive symptomatology from tinnitus-specific impacts.
The methods are described more fully in a previously published protocol cited by the authors. No ethical approval was required for this design. The authors report that all relevant data are contained within the manuscript and its supporting information files. The study applied specific interpretive coding decisions (notably the treatment of tinnitus-named items as b240) and evaluated an alternative coding strategy to assess its effect on overlap estimates.
Using the ICF framework, the study found nontrivial content overlap between commonly used tinnitus distress and depressive symptom questionnaires, with seven shared ICF second-level domains and wide variation in overlap at the instrument level. These findings support deliberate questionnaire selection and mindful interpretation in clinical practice and research focused on tinnitus and depression.