Condition
    Moderate Evidence
    Effectiveness 3/5

    N-Acetyl Cysteine (NAC) for Obsessive-Compulsive Disorder

    NAC is the most-studied supplement in OCD — a meta-analysis of randomised trials shows modest benefit as an add-on to standard treatment — but results are inconsistent between studies, and it never replaces ERP therapy or prescribed medication.

    Overview

    NAC is the most-studied supplement in OCD — a meta-analysis of randomised trials shows modest benefit as an add-on to standard treatment — but results are inconsistent between studies, and it never replaces ERP therapy or prescribed medication.

    Verdict

    Mixed evidence

    How It Works

    NAC modulates glutamate, the excitatory neurotransmitter implicated in OCD's cortico-striatal circuits, and replenishes glutathione, reducing oxidative stress in those same pathways. This dual action gives it a plausible mechanism where standard serotonin-only thinking falls short.

    Dosing & Protocol

    Typical dose

    Recommended dose
    1,200-3,000 mg daily, divided, typically as an adjunct to standard care
    Expected timeframe
    8-12 weeks (trials ran 10-12 weeks)

    Protocol

    form
    N-acetylcysteine capsules
    duration
    12-16 weeks; the negative trials were shorter or underpowered
    co factor
    Use as an add-on to an established SSRI dose and to exposure and response prevention. Take with meals to limit nausea. Evidence is mixed: several randomised trials found no advantage over placebo, while others showed modest Y-BOCS reductions.
    titration
    Increase by 600 mg/day each week to 2400-3000 mg/day in two divided doses
    starting dose
    600 mg twice daily with food

    Evidence

    What the studies say

    Several randomised placebo-controlled trials of NAC (1,200-3,000 mg/day) as augmentation to SSRIs in OCD have been published, with a meta-analysis finding a modest overall benefit but significant inconsistency — some positive, some null. Trial quality is moderate and sample sizes small. It ranks among the better-evidenced supplements in psychiatry, yet remains strictly an adjunct.

    Mitochondrial modulators for obsessive-compulsive and related disorders: a systematic review and meta-analysis

    Score: 8/10
    2022
    meta_analysis
    n=629

    Kishi T, et al.

    In conclusion, N-acetylcysteine was beneficial in the treatment of obsessive-compulsive and related disorders. However, further study with larger samples is necessary to confirm this finding.

    View source

    N-acetyl cysteine (NAC) augmentation in the treatment of obsessive-compulsive disorder: a phase III, 20-week, double-blind, randomized, placebo-controlled trial

    Score: 8/10
    2022
    rct

    Sarris J, Byrne G, Castle D

    A modified intention-to-treat analysis of the primary outcome found no evidence that NAC reduced symptoms of OCD measured on the Yale-Brown Obsessive-Compulsive Scale, relative to placebo.

    View source

    Glutamatergic medications as adjunctive therapy for moderate to severe obsessive-compulsive disorder in adults: a systematic review and meta-analysis

    Score: 7/10
    2021
    meta_analysis
    n=759

    Hadi F, et al.

    Augmentation of glutamatergic medications with SSRIs are beneficial in obsessive-compulsive patients, no harmful significant differences in any safety outcome were found between the groups.

    View source

    N-acetylcysteine augmentation in treatment-resistant obsessive-compulsive disorder: a randomized double-blind placebo-controlled trial

    Score: 8/10
    2017
    rct
    n=40

    Costa DLC, Diniz JB, Requena G +5 more

    NAC did not outperform placebo on the primary Yale-Brown obsessive-compulsive scale outcome

    View source

    The safety and efficacy of N-acetylcysteine as an augmentation in the treatment of obsessive-compulsive disorder in adults: a systematic review and meta-analysis of randomized clinical trials

    Score: 6/10
    2024
    meta_analysis

    Eghdami S, Eissazade N, Heidari Mokarar M

    Augmentation of NAC with SSRIs may benefit patients with moderate to severe OCD. However, it is necessary to conduct additional multi-center trials over extended periods.

    View source

    Safety

    Caveats

    GI upset and flatulence are common. Discuss with your prescriber before combining with psychiatric medication. Never delay ERP or medication to try supplements first.

    Less likely to help if

    People with long-standing treatment-resistant OCD who are not engaged in ERP, and those with hoarding-predominant presentations.

    Medical Disclaimer

    The information provided on this website is for educational and informational purposes only and is not intended as a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition or before starting any supplement regimen.

    Individual results may vary. The statements on this website have not been evaluated by the Food and Drug Administration. Products and information are not intended to diagnose, treat, cure, or prevent any disease.