N-acetylcysteine,
does it really help with Relief of obsessive-compulsive symptoms measured by Y-BOCS when added to existing treatment in adults?
research showsThe 20-week Y-BOCS difference was 0.53 points (95% CI -2.18 to 3.23), the Costa trial found -1.30 (-6.49 to 3.89), the Afshar trial found -5.14 (-7.05 to -3.23), and the five-to-eight-week pooled MD was positive at -2.95 (-5.87 to -0.04). Results conflict and do not exclude clinically meaningful benefit, so the grade is D with 35 points, not F.
ads claimMarketing can turn antioxidant and glutamate-modulating mechanisms into a claim that NAC stops obsessive thoughts. The identified trials evaluated off-label augmentation of existing SSRI or SRI treatment, not monotherapy or replacement of prescribed treatment.
Useful facts when choosing a product
- OCD trials generally added NAC doses ranging from 600 to 3,000 mg per day to existing SSRI or SRI treatment; they did not establish supplement monotherapy.
- NAC is used as a medicine for acetaminophen poisoning and certain respiratory indications, but those medical uses do not establish efficacy of a supplement for OCD.
- Oral NAC can cause nausea, diarrhea, abdominal pain, heartburn, and an unpleasant odor or taste, while rash or hypersensitivity is uncommon.
- Content, formulation, quality, and delivered exposure can vary across supplements, and prescribed psychiatric treatment should not be stopped or replaced with NAC without clinical supervision.
Chamgap Semantic Classification Code
Candidate index · review held
S.n-acetylcysteine.oral.obsessive-compulsive-symptoms-measured-by-y-bocs-when-added-to-existing-treatment.relieve.MULTISupplements and nutraceuticals > N-acetylcysteine > Oral > obsessive-compulsive symptoms measured by Y-BOCS when added to existing treatment > Symptom-relief claim > Multiple: primary unresolved
An automated migration candidate, not an issued permanent code; exact claim scope remains under review. This machine-generated migration candidate helps retrieval but is not a permanent assignment. The original verdict ID and URL remain authoritative.
What the research actually shows
In the 98-person multicenter 20-week phase III trial, the week-20 between-group Y-BOCS difference was 0.53 points (95% CI -2.18 to 3.23, P=.70), and anxiety, depression, quality of life, functioning, and other secondary outcomes also did not improve. Other 16-week trials did not establish benefits in total scores or response. The Brazilian OCD guideline does not recommend NAC on the basis of better-quality negative trials, and the 2025 update guideline concluded that current evidence does not support efficacy. A five-to-eight-week signal in the 2024 six-trial meta-analysis and a positive 35-person pilot in 2026 remain, but are too small to overturn the best trial and guideline conclusions.
Why this is classified as D (35)
The 20-week Y-BOCS difference was 0.53 points (95% CI -2.18 to 3.23), the Costa trial found -1.30 (-6.49 to 3.89), the Afshar trial found -5.14 (-7.05 to -3.23), and the five-to-eight-week pooled MD was positive at -2.95 (-5.87 to -0.04). Results conflict and do not exclude clinically meaningful benefit, so the grade is D with 35 points, not F.
Counterpoint. People who remain symptomatic despite an adequate SSRI or clomipramine course and exposure-and-response-prevention therapy should first discuss better-established augmentation strategies with a specialist. If NAC is tried, its off-label adjunctive status and explicit response and stopping criteria should be clear. Grade-independent note: Brazilian and Indian guidance recommends against NAC use. These recommendations and adverse-effect information are not used to determine the efficacy grade.
Rejudgment record. Cross-check revision — The 20-week Y-BOCS difference was 0.53 points (95% CI -2.18 to 3.23), the Costa trial found -1.30 (-6.49 to 3.89), the Afshar trial found -5.14 (-7.05 to -3.23), and the five-to-eight-week pooled MD was positive at -2.95 (-5.87 to -0.04). Results conflict and do not exclude clinically meaningful benefit, so the grade is D with 35 points, not F.
Sub-claim grades by effect
This ingredient is marketed for several effects. A single overall grade blends strong and weak claims together, so each effect is graded separately here. The overall grade reflects the strongest disconfirming or core claim.
| Effect (sub-claim) | Grade | Basis |
|---|---|---|
| Reduction of total obsessive-compulsive symptoms on Y-BOCS when added to existing treatment | D | Guidelines do not support efficacy or recommend use, and the best 98-person 20-week phase III trial had a null 0.53-point Y-BOCS difference. |
| Reduction of obsession symptoms when added to existing treatment | D | Guidelines do not support NAC efficacy or recommend use, and the best trial and pooled obsession outcomes did not establish a consistent benefit. |
| Reduction of compulsion symptoms when added to existing treatment | D | Guidelines do not support NAC efficacy or recommend use, and the best trial and pooled compulsion outcomes did not establish a consistent benefit. |
Cross-check — AI research and Codex final gate
Evidence Table
| Study | Design | Sample | Funding | Endpoint | Result | Weight |
|---|---|---|---|---|---|---|
| Eghdami S et al. 2024 | Systematic review and meta-analysis of randomized clinical trials | Six randomized trials and 195 participants | Funded by Iran University of Medical Sciences | Total Y-BOCS, obsession and compulsion subscales, and adverse events | The five-to-eight-week total Y-BOCS mean difference was -2.95, while results beyond 12 weeks and on both subscales were not significant. | Key synthesis with a small sample and inconsistency |
| Costa DLC et al. 2017 | Sixteen-week randomized double-blind placebo-controlled augmentation trial | Forty treatment-resistant adults recruited | Funding was not reported in the PubMed abstract | Change in total Y-BOCS at 16 weeks | NAC 3,000 mg/day did not differ from placebo in Y-BOCS reduction (P=.92). | Direct longer-term null adult trial |
| Afshar H et al. 2012 | Twelve-week randomized double-blind placebo-controlled augmentation trial | Forty-eight patients with treatment-refractory OCD | Funding was not reported in the PubMed abstract | Y-BOCS change and full response defined as at least 35% reduction | Adjunctive NAC up to 2,400 mg/day improved Y-BOCS and full-response rates versus placebo. | Small positive signal contributing to inconsistency |
| Sarris J et al. 2022 phase III trial | Multicenter 20-week randomized double-blind placebo-controlled phase III augmentation trial | Ninety-eight participants with DSM-5 obsessive-compulsive disorder | Funded by the Australian National Health and Medical Research Council | Total Y-BOCS at 20 weeks plus anxiety, depression, quality of life, and functioning | The week-20 between-group Y-BOCS difference was null at 0.53 points (95% CI -2.18 to 3.23, P=.70), and secondary outcomes did not improve. | Best large direct null trial |
| Oliveira MVS et al. 2023 Brazilian OCD guideline | Evidence review and clinical practice guideline for pharmacological treatment of adult obsessive-compulsive disorder | Guideline synthesis of four randomized NAC trials | Brazilian Research Consortium on Obsessive-Compulsive Spectrum Disorders | Efficacy and recommendation for NAC augmentation | Did not recommend NAC because positive trials had serious methodological problems and the better-quality trials were negative. | Boundary evidence recommending against use |
| Arumugham SS et al. 2025 update guideline | Updated clinical practice guideline for obsessive-compulsive disorder | Guideline synthesis of small NAC trials and meta-analyses | Indian Psychiatric Society guideline update | Efficacy of NAC augmentation | Concluded that current evidence does not support NAC efficacy in obsessive-compulsive disorder. | Boundary evidence from a guideline finding no efficacy support |
| Askari S et al. 2026 pilot trial | Twelve-week randomized double-blind placebo-controlled pilot trial | Thirty-five adults with moderate-to-severe obsessive-compulsive disorder | Funded by Iran University of Medical Sciences | Total Y-BOCS, subscales, and cognitive function | The time-by-group interaction for total Y-BOCS was positive, but this was a 35-person pilot and cognitive outcomes did not differ between groups. | Current small positive signal |
Receipt — 7 References
All 7 cited sources were verified for existence at the original page (as of 2026-07-21).
Final verification and publication gate: Codex · Evidence date: 2026-07-21 · Corrections: none
Cite this verdict
[Chamgap] N-acetylcysteine x adjunctive treatment of adult obsessive-compulsive disorder — Evidence Grade D·35. 7 cited sources checked. Source: https://chamgap.com/en/verdicts/mood/n-acetylcysteine-adjunct-ocd-y-bocs-symptoms/ · CC BY 4.0CC BY 4.0 — free to use with attribution; do not distort grades, numbers, or verdict meaning.
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