Morgenstern 1997.

Study characteristics
Methods	A 2‐armed (Gingko biloba and placebo), parallel‐group randomised controlled trial with 12 weeks duration of treatment and 4, 8 and 12 weeks duration of follow‐up
Participants	Location: Hamburg, Germany Setting: single‐centre study, St. Georg Hospital, Hamburg, Germany Sample size: Number randomised: 49 in Ginkgo biloba group and 50 in placebo group Number completed: 35 in Ginkgo biloba group and 38 in placebo group Participant baseline characteristics: Age: over 18 years Gender: not reported Other characteristics: baseline tinnitus loudness was 42.2 dB HL in the intervention group and 44.3 dB HL in the control group. Mean tinnitus duration in all participants was 4.5 years. All participants had normal hearing at 3 neighbouring frequencies in the audiogram. Baseline data for tinnitus symptom severity, tinnitus characteristics, anxiety and depression were not reported. Inclusion criteria: over 18 years old and chronic subjective tinnitus, normal hearing at 3 neighbouring frequencies in the audiogram Exclusion criteria: objective tinnitus, middle ear pathology, reproducibility of the transient evoked otoacoustic emissions at the intake examination < 85%, latency extensions or pathological wave models of earlier brain stem auditory evoked potentials (BAEPs), severe organic diseases, alcohol or drug abuse, pregnancy
Interventions	Intervention group: Ginkgo biloba coated tablets (40 mg of Gingko special extract EGb 761, a dry extract made from gingko biloba leaves (35 to 67:1), set to 9.6 mg gingko flavone glycoside and 2.4 mg of terpene lactone), 1 tablet 3 x day (120 mg), 12 weeks Comparator group: placebo coated tablets, 1 tablet 3 x day, 12 weeks Use of additional interventions: none reported
Outcomes	Primary outcome: change in tinnitus loudness measured with audiometric methods in the ear with louder tinnitus at 4, 8 and 12 weeks Secondary outcomes: change in tinnitus intensity measured with a scale of Subjective Evaluation of Tinnitus Intensity (0 to 5), click‐evoked otoacoustic emissions (OAEs) at 4, 8 and 12 weeks
Funding sources	No information provided
Declarations of interest	No information provided
Notes	—
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Information on methods of random sequence generation not reported in the manuscript.
Allocation concealment (selection bias)	Unclear risk	Information not reported in the manuscript.
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Double‐blinding stated, methods not described.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Information not reported in the manuscript.
Incomplete outcome data (attrition bias) All outcomes	High risk	There are no data regarding the primary outcome measure for 14 patients in the intervention group and 12 in the control group at 12 weeks. Dropout is not explained.
Selective reporting (reporting bias)	Unclear risk	No values for secondary outcome measures are reported. Only brief statements regarding whether those improved or not.
Other bias	Unclear risk	This is an abbreviated version of the full study report, which is not available. No prospective protocol available. No funding sources and declarations of interest reported.