Table 2.

Overview of challenges in tinnitus research and proposed future direction towards a cure for tinnitus.

Challenges	Proposed directions
Tinnitus Heterogeneity
Lack of understanding of tinnitus heterogeneity and no clearly defined subtypes	Systematic reviews of studies investigating tinnitus subphenotypes Standardization in tinnitus assessment and international collaborations to create large tinnitus-specific databases Exploratory analyses investigating multiple dimension of tinnitus heterogeneity in large samples to identify important phenotypes
Epidemiology, Risk Factors & Prevention
Varying prevalence estimates and associations between tinnitus and other factors	Standardization of tinnitus definition Systematic reviews and retrospective analysis of existing databases Prospective analytical observational studies from nationally representative populations
Tinnitus Mechanisms
Unknown underlying pathophysiology and lack of replicable functional, structural and neurochemical neural markers and genetic markers of tinnitus	Systematic reviews on methods and results of previous studies Standardization of data acquisition and analysis methods Large studies investigating suspected theories Replication of existing studies Selection of clear phenotypes for inclusion
Tinnitus Assessment
Lack of standardization in tinnitus assessment (what and how)	Systematic reviews to identify the most useful and reliable measures Collaboration among research groups and consensus projects to standardize tinnitus assessment
Treatments
Low evidence from clinical trials	Large randomized controlled clinical trials based on sample power calculations Pre-registration Consensus on outcome measures Treatment predictors and personalized medicine Single-case design methodology Selection of clear phenotypes for inclusion