The majority of literature examining tinnitus retraining therapy (TRT) came from case series and case reports and "is inconclusive due to the unavailability of controls, unclear patient selection criteria, the variability of TRT methods being implemented and the variability in the criteria of treatment outcomes being employed" (Level 4 Evidence, p. 13). Only one unpublished randomized controlled trial found that "at 18 months, 87% of patients in TRT programs had significant improvement compared to 58% among those using tinnitus masking therapy" (Level 1 Evidence, p. 13). However, these results should be interpreted with caution since the study population included was limited to veterans and the study has not been replicated.
