Yarmohammadi 2007.

Study characteristics
Methods	A 2‐armed (Ginkgo biloba and placebo), parallel‐group randomised controlled trial with 2 weeks duration of treatment and 2 weeks duration of follow‐up
Participants	Location: Teheran, Iran Setting: single‐centre study, otolaryngology clinic Sample size: Number randomised: 30 in Ginkgo biloba group and 30 in placebo group Number completed: 30 in Ginkgo biloba group and 30 in placebo group Participant baseline characteristics: Age (mean (SD) years): 51.2 (SD 1.9) in Ginkgo biloba group versus 51.5 (SD 1.7) years in placebo group Gender (male/female, n): 14/16 in Ginkgo biloba group versus 12/18 in placebo group Other characteristics: baseline tinnitus symptom severity was not reported. Mean tinnitus duration was 51.2 (SD 9.1) months in the intervention group and 56.9 (SD 7.9) months in the placebo group. Tinnitus was unilateral in 56.7% of participants in the intervention group and 66.7% participants in the placebo group and bilateral in the rest of the participants. All participants had normal hearing. Inclusion criteria: patients diagnosed with tinnitus and with no reduction of hearing who had a normal MRI were included in the study Exclusion criteria: none
Interventions	Intervention group: Ginkgo T.D. tablets (Tolid Darou Pharmaceutical Company), 40 mg, twice daily for 2 weeks Comparator group: placebo tablets, 40 mg, twice daily for 2 weeks Use of additional interventions: none reported
Outcomes	Primary outcome: improvement in severity of tinnitus measured with undefined questionnaire at 2 weeks Secondary outcomes: none
Funding sources	Quote: "The authors would like to thank Tolid Darou Pharmaceutical Company for providing the medication and the placebo."
Declarations of interest	No information provided
Notes	—
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	High risk	Quote: “The ginkgo T.D. tablets and the placebos were placed in an equal number of paper bags—30 bags containing ginkgo T.D. and 30 bags containing the placebo, labelling the bags with numbers. The doctor randomly administered the contents of the bags to the patients.”
Allocation concealment (selection bias)	Unclear risk	Bags with tablets but concealment methods not described (doctor randomly administered the contents of the bags to the patients).
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Quote: "In this study, the doctor and patients were unaware of the type of medication, with only the second co‐researcher in charge of numbering and packaging the bags being aware."
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Information not reported in the manuscript.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Data for all participants reported.
Selective reporting (reporting bias)	High risk	Questionnaire for tinnitus severity was not described; authors interpreted the result as no change, improvement and exacerbation but it is unclear what the criteria were for such classification.
Other bias	Unclear risk	No prospective protocol available. No declarations of interest reported.

AD: Alzheimer's disease; CT: computerised tomography; MRI: magnetic resonance imaging; SD: standard deviation; SKT: Short Cognitive Performance Test (Syndrom‐Kurztest); THI: Tinnitus Handicap Inventory; VaD: vascular dementia