To determine whether there are well established treatments for tinnitus, whether there are promising treatments that deserve further research, and whether research procedures in this area can be improved.

Studies were sought from the following sources: MEDLINE from 1966 to 1998 using the keywords 'tinnitus' and 'randomized clinical trials'; personal files; reference lists from studies retrieved; and a search of OLD MEDLINE for 'tinnitus'.

Study designs of evaluations included in the review

Randomised controlled trials (RCTs) of drug or non-drug treatment for subjective tinnitus were included if they provided sufficient detail for analysis.

Specific interventions included in the review

The following interventions were studied: tocainide, iontophoresis of lidocaine, carbamazepine, amino-oxy-acetic-acid, benzodiazepines, tricyclic antidepressants, gingko, miscellaneous drugs, maskers, electrical stimulation, magnetic stimulation, ultrasound, biofeedback, acupuncture, hypnosis, psychotherapy, miscellaneous non-drug treatments; anti-histamines; and placebo treatments. 'Waiting list' placebo treatments and studies of intravenous lidocaine were excluded.

Participants included in the review

Patients with tinnitus. Studies with tinnitus as a side effect of treatment were excluded as well as studies limited to a single otological or neurological disorder.

Outcomes assessed in the review

The following outcomes were included: patient's global assessment; tinnitus sensation; tinnitus loudness; tinnitus impact; sleep disturbance; emotional distress scores; and tension.

How were decisions on the relevance of primary studies made?

The author does not state how the papers were selected for the review, or how many of the reviewers performed the selection.

No formal assessment of validity was performed. However, the author discussed a number of methodological flaws.

The author does not state how the data were extracted for the review, or how many of the reviewers performed the data extraction.

How were the studies combined?

The studies were combined in a narrative review.

How were differences between studies investigated?

The author does not state how differences between the studies were investigated.

Sixty-nine RCTs were included. The number of participants was unclear.

Statistical significance of results was not consistently reported hindering interpretation of results.

Methodological flaws mentioned by the author of the review include: incorrect method of statistical analysis, incomplete reporting; potential confounding effect of differing intensity of clinician interaction; lack of or compromising of patient blinding; high drop-out rates; lack of intention-to-treat analysis; inadequate implementation of intervention; and lack of consensus regarding measurement of response .

Tocainide (6 RCTs): inconsistent results. One RCT reported statistically significantly greater 'relief' with tocainide while 5 RCTs reported no significant effect.

Iontophoresis of lidocaine (2 RCTs): no difference in outcome between treatment groups.

Carbamazepine (4 RCTs): no benefit.

Amino-oxy-acetic-acid (2 RCTs with 142 patients): inconsistent results. One trial with 10 patients reported benefit , a larger trial reported no benefit.

Benzodiazepines (4 RCTs): inconsistent results. One RCT of diazepam showed no benefit. One RCT with many missing details reported that clonazepam and oxazepam outperformed anti- histamines. One RCT of alprazolam reported reduced tinnitus loudness in the treatment group.

Tricyclic antidepressants (3 RCTs): inconsistent results. One RCT reported no difference compared to placebo. Two RCTs reported greater benefit for antidepressants compared to placebo.

Gingko (2 RCTs): response no different from placebo.

Maskers (6 RCTs): One RCT reported significant improvement for maskers compared to inactive device, one RCT favoured maskers over hearing aids with respect to falling asleep, one RCT favoured maskers over acupuncture. One RCT reported no difference between maskers and cognitive therapy and one RCT reported masking to be inferior to self-hypnosis.

Electrical stimulation (3 RCTs): no benefit.

Magnetic stimulation (3 RCTs): inconsistent results with one RCT favouring stimulation over placebo device and one RCT finding no benefit over placebo magnets.

Ultrasound (2 RCTs): inconsistent results.

Biofeedback (5 RCTs): inconsistent results with two negative RCTs (one consisted on 2 patients), one RCT reporting few small differences and one RCT favouring biofeedback.

Acupuncture (6 RCTs): no statistically significant difference.

Hypnosis (3 RCTs): inconsistent results. Two RCTs favoured hypnosis (over counselling and over masking and 'attentiveness') and one RCT reported no difference between 3 types of hypnosis.

Psychotherapy: 3 RCTs reported no difference compared to masking or hypnosis. Other RCTs compared different types of psychotherapy.

Miscellaneous drugs were studies in 14 RCTs and miscellaneous non-drug interventions in 4 RCTs.

Non-specific support and counselling are probably helpful, as are tricyclic antidepressants in severe cases. Benzodiazepine, newer antidepressants, and electrical stimulation deserve further study. Future tinnitus therapeutic research should emphasis adequate sample size, open trials before RCTs, careful choice of outcome measures and long-term follow-up.

The aims and inclusion criteria were stated. Some methodological flaws in the primary studies were mentioned.

By limiting the literature search to one databases some relevant studies may have been omitted.

No specific attempts were made to locate unpublished data so publication bias is a possibility. Methods used to select primary studies or extract data were not reported. Only brief details were given of the primary studies and no formal assessment of validity was conducted. In particular, number of patients enrolled and methods used to determine outcomes and results in primary studies were not reported in adequate detail. Without more comprehensive details of the included studies and an assessment of validity an assessment of the evidence cannot be undertaken.

Practice: see under 'Authors' conclusions' above.

Research: see under 'Authors' conclusions' above.

This is a critical abstract of a systematic review that meets the criteria for inclusion on DARE. Each critical abstract contains a brief summary of the review methods, results and conclusions followed by a detailed critical assessment on the reliability of the review and the conclusions drawn.