Table 3.

Summary of included reviews: N-acetylcysteine for obsessive-compulsive and related disorders.

Authors (Year)	Type	Inclusion	No. Studies (Study Size)	Conclusion
Oliver el al. (2015) [11]	SR	Human clinical trials or case reports involving diagnosed OCD or related disorders in which NAC was prescribed.	Total = 11 (n = 206): OCD = 3 (n = 46); TTM = 4 (n = 94); Onychophagia = 2 (n = 28); Excoriation = 2 (n = 38)	Treatment with 2,400-3,000 mg/d of NAC in the included trials was found to reduce the severity of symptoms and demonstrate good tolerability with minimal adverse effects.
Smith et al. (2016) [28]	SR	Placebo RCTs investigated NAC for OCD and related disorders with behavioural outcome measures.	Total = 4 (n = 162): OCD = 1 (n = 48); TTM = 2 (n = 89); Onychophagia = 1 (n = 25)	Results remain inconclusive, but NAC may still be useful as a treatment for OCD and related disorders on an individual level given its safety records.
Minarini et al. (2017) [16]	SR	Clinical trials that assessed NAC use as the independent variable and clinical outcomes related to a psychiatric disorder.	Total = 20 (n = 421): OCD = 7 (n = 149); TS = 1 (n = 31); TTM = 4 (n = 92); Excoriation = 5 (n = 101); Onychophagia = 3 (n = 48)	Promising results were found in trials testing the use of NAC as an add-on treatment for excoriation. Preliminary evidence warrants further investigation of the possible effectiveness NAC for OCD and related disorders.

Abbreviation. Meta-analysis (MA); N-acetylcysteine (NAC); obsessive-compulsive disorder (OCD); randomised control trial (RCT); systematic review (SR); tourette syndrome (TS); trichotillomania (TTM).