Background: Inferior efficacy of an antidepressant in a head-to-head clinical trial may be caused by lower dosing; consequently, 'unfair' dosing may be a potential source of bias. The issue of dose comparability should therefore be considered in evaluations of the quality and validity of meta-analyses and individual studies on antidepressants.

Objectives: The aim of our study was to assess whether dose comparability is addressed in Cochrane reviews (CRs) on head-to-head trials comparing antidepressants.

Methods: A systematic literature search was carried out to identify relevant CRs. To fulfil inclusion criteria, the CR had to include at least one head-to-head trial comparing antidepressants. A total of 62 potentially relevant CRs were screened, and 18 relevant CRs were subsequently identified. Data were extracted by one person and checked by a second. They assessed (i) whether dose comparability was recognised as a relevant issue in the first place (i.e. mentioned in the background section); (ii) whether 'fair dosing' was an inclusion criterion for studies in the CRs and doses of study medications were reported in the tables; (iii) whether dose comparability was explicitly referred to in the presentation and discussion of results.

Results: (i) Only two of 18 CRs addressed the issue of dose comparability in the background section. (ii) 'Fair' dosing was not an inclusion criterion for studies in any CR. Fourteen CRs presented the applied doses in the tables. (iii) (Lacking) dose comparability was discussed as a potential influence on the review's outcome in three CRs, yet not further analysed.

Conclusions: Dose comparability has so far not received much attention in CRs on antidepressants, thus neglecting a potential source of bias. Further discussion is needed on how to deal with this issue in the future.