Results on whether N-acetylcysteine (NAC) ameliorates depression in patients with psychiatric problems, such as bipolar disorder and major depressive disorder, remain inconsistent, and several new studies have recently been published. Thus, we conducted an uptodated meta-analysis to evaluate the efficacy of NAC against depression.

This systematic review and meta-analysis included randomized controlled trials where NAC was used to treat depression. The present study adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. PubMed, Embase (Ovid), and Cochrane were searched for relevant articles. A random-effects model was used to evaluate the primary outcome—efficacy of NAC in ameliorating depression.

This review included 12 studies (904 patients with depression). The daily dose of NAC in the included studies ranged from 1000 to 3000 mg. The duration of NAC treatment ranged from 8 to 24 weeks. A significant difference was noted between NAC and placebo in terms of the change in mean depression score from baseline to treatment conclusion (standardized mean difference = −0.24; 95 % confidence interval (CI) = −0.44 to −0.05; I² = 45 %; P = .02).

Our findings indicate that adjunctive NAC can ameliorate depressive symptoms in patients with psychiatric problems, particularly bipolar disorder. However, large-scale clinical trials were needed to substantiate our results due to the wide CI value.