NAC and Body-Focused Repetitive Behaviors (BFRBs)

Body-focused repetitive behaviors (BFRBs) such as trichotillomania (hair-pulling), excoriation disorder (skin-picking), and onychophagia (nail-biting or biting on clothes) can be distressing, chronic, and difficult to treat. Although these behaviors fall under the obsessive-compulsive and related disorders category in the DSM-5, they are often misunderstood and underdiagnosed.

A growing body of research supports the use of N-acetylcysteine (NAC), a relatively safe, over-the-counter supplement, as a promising adjunct treatment for these conditions. NAC is most well-known as a mucolytic and an antidote for acetaminophen toxicity, but it also shows strong therapeutic potential for psychiatric conditions, particularly those involving impulse control and compulsive behaviors.

It is also important to note that BFRBs may be exacerbated by stimulant medications commonly prescribed for Attention-Deficit/Hyperactivity Disorder (ADHD). While stimulants can improve attention and focus, they may also increase nervous system arousal and exacerbate repetitive motor behaviors in some individuals, particularly those predisposed to BFRBs. Case reports and clinical observations have noted a link between the initiation or dose increase of ADHD medication and the onset or worsening of skin-picking or hair-pulling behaviors (Mansueto et al., 2020; Grant & Chamberlain, 2016). Clinicians treating co-occurring ADHD and BFRBs must weigh the benefits of stimulant treatment against the potential for increased compulsive behaviors, and consider adjunct supports such as NAC.

Mechanism of Action: How NAC Works

Glutamate Regulation
NAC is a precursor to the amino acid L-cysteine, which is converted into cystine in the body. Cystine plays a central role in regulating glutamate, the brain's main excitatory neurotransmitter.

Specifically, cystine enters glial cells through the cystine-glutamate antiporter (system Xc-), which releases glutamate into the extracellular space. This extracellular glutamate activates metabotropic glutamate receptors (mGluR2/3), which in turn inhibit excessive synaptic glutamate release.

This mechanism helps stabilize glutamate levels in brain circuits implicated in reward, habit formation, and impulse control, especially the cortico-striato-thalamo-cortical (CSTC) circuit. In individuals with BFRBs, this circuit is believed to be dysregulated, leading to heightened compulsive urges.

By restoring glutamate homeostasis, NAC may reduce the intensity of urges and compulsions, allowing individuals to exert more cognitive control over their behaviors.

Precursor to Glutathione: Reducing Oxidative Stress and Neuroinflammation
NAC is also the rate-limiting precursor to glutathione (GSH), the body's most powerful antioxidant. Glutathione is essential for detoxifying reactive oxygen species and maintaining redox balance in the brain.

Increased oxidative stress and neuroinflammation have been implicated in several psychiatric disorders, including obsessive-compulsive disorder (OCD), depression, and body-focused repetitive behaviors. By boosting glutathione levels, NAC can reduce this oxidative burden and support healthier brain function.

This dual action, glutamate modulation and antioxidant support, makes NAC uniquely suited for treating disorders like trichotillomania and excoriation disorder.

Research

Hair Pulling (Trichotillomania):
A landmark double-blind randomized controlled trial (RCT) by Grant et al. (2009) found that 56% of participants taking NAC (1,200–2,400 mg/day) experienced significant improvement in symptoms, compared to only 16% in the placebo group. Improvements included decreased frequency, intensity, and associated distress of hair-pulling behaviors.

Skin Picking (Excoriation Disorder):
In another RCT, Grant et al. (2016) found that NAC significantly reduced skin-picking severity with minimal side effects. Participants taking NAC showed greater reductions in urges and frequency of picking compared to those receiving a placebo. Some reports suggest that combining NAC with cognitive-behavioral therapy (CBT) or habit reversal training (HRT) results in even better outcomes.

Nail Biting & Biting on Clothes (Onychophagia):
Although research is more limited, a RCT by Ghanizadeh et al. (2013) demonstrated that NAC significantly reduced nail-biting behavior in children and adolescents over a 2-month period. Recent reviews and case studies also support its use for oral BFRBs, such as biting on clothes or objects, especially in pediatric and neurodiverse populations.

Typical Dosing, Safety, and Practical Use

Typical Adult Dose: 1,200–2,400 mg/day, often divided into two doses.
Typical Titration: Start low (e.g., 600 mg/day) and increase gradually to minimize gastrointestinal side effects.
Safety Overview: NAC is generally well tolerated. Side effects are rare but may include mild gastrointestinal discomfort or headaches.
NAC supplementation is available in capsules, powders, or effervescent tablets.

For children and adolescents, studies suggest starting with a lower dose of around 600 mg per day. This may be gradually increased up to 1,200 mg/day based on tolerance and clinical guidance (Ghanizadeh et al., 2013). Pediatric dosing should always be customized to the child's weight, symptom severity, and overall health profile under professional supervision.

At Well Mind Body, we believe in looking at the whole person when developing a treatment plan. Our integrative approach combines evidence-based therapy with targeted nutritional support.

If you are looking for a high quality NAC supplement. one our favorites is NAC from XYMOGEN. This supplement can be order here.

Always consult a healthcare provider before beginning NAC or any other supplement, especially in individuals with asthma, bleeding disorders, or those taking medications that may interact with glutathione metabolism.

Here at Well Mind Body we recommend third-party tested supplements that meet high quality standards to ensure safety, purity, and efficacy. Our goal is to support mental health through both psychological and physiological pathways, helping our clients build sustainable well-being from the inside out.

References

Dean, O., Giorlando, F., & Berk, M. (2011). N-acetylcysteine in psychiatry: Current therapeutic evidence and potential mechanisms of action. Journal of Psychiatry & Neuroscience, 36(2), 78–86. https://doi.org/10.1503/jpn.100057

Ghanizadeh, A., Bazrafshan, A., & Firoozabadi, A. (2013). N-acetylcysteine versus placebo for treating nail biting: A double-blind randomized placebo-controlled clinical trial. Anti-Inflammatory & Anti-Allergy Agents in Medicinal Chemistry, 12(3), 234–237. https://doi.org/10.2174/1871523011312030009

Grant, J. E., Chamberlain, S. R., Redden, S. A., & Leppink, E. W. (2016). N-acetylcysteine in the treatment of excoriation disorder: A randomized clinical trial. JAMA Psychiatry, 73(5), 490–496. https://doi.org/10.1001/jamapsychiatry.2016.0060

Grant, J. E., Odlaug, B. L., Chamberlain, S. R., & Kim, S. W. (2009). N-acetylcysteine, a glutamate modulator, in the treatment of trichotillomania: A double-blind, placebo-controlled study. Archives of General Psychiatry, 66(7), 756–763. https://doi.org/10.1001/archgenpsychiatry.2009.60

Kashetsky, N., Wong, A., Lam, J. M., Wong, S. M., & Mukovozov, I. M. (2023). Efficacy of N-acetylcysteine in trichotillomania (hair-pulling disorder), skin-picking disorder and onychophagia (compulsive nail-biting). Journal of the European Academy of Dermatology and Venereology, 37(1), e73–e76. https://doi.org/10.1111/jdv.18508

Lee, D. K., & Lipner, S. R. (2022). The potential of N-acetylcysteine for treatment of trichotillomania, excoriation disorder, onychophagia, and onychotillomania: An updated literature review. International Journal of Environmental Research and Public Health, 19(11), 6370. https://doi.org/10.3390/ijerph19116370

Mansueto, C. S., Stemberger, R. M., & Golomb, R. G. (2020). Body-focused repetitive behaviors and stimulant medications: Understanding the connection. Cognitive and Behavioral Practice, 27(2), 229–239.