Benefits of N-acetyl cysteine in treating Trichotillomania — Donovan Hair Clinic

Trichotillomania is a hair pulling disorder. I have reviewed the DSM Criteria in the past.

Current evidence suggests that habit reversal training may be among the most consistently effects treatments for helping patients with trichotillomania. Pharmacologic agents with N-acetyl cysteine (NAC), chlomipramine and olanzapine may be helpful based on trials to date.

Although behavioural therapy and treatment of associated psychiatric and psychological issues should not be ignored when addressing TTM, NAC is a good option for many practitioners to consider for adults patients given its good safety. Nausea, diarrhea GI upset, rash can occur but are not common.

Kashetsky et al. 2022

Authors of a new report set out to summarize how well NAC works for treating trichotillomani as well as skin picking disorder and onychophagia (nail biting). Here I will focus on trichotillomania.

The authors found 60 patients in the literature with a mean age of 25 years (range 11 to 65). 40 % of patients were pediatric and 60 % were adults. 88 % of patients were female. 56 % of patients had co-existing psychiatric disorders. Patients were treated with doses ranging from 600 mg to 2400 mg for a range of time (1-10 months). 8 % were also using medications at the time of their NAC treatment and this was mainly SSRI medications.

Overall, about 70 % of adults and 40 % of children responded to NAC. The response time was 2.1 months (range 0.5 to 6 months). 25 % of patients recurred. 20 % of patients had side effects including nausea, diarrhea, rash, gas, depression and difficulty swallowing pills.


This is a nice review of the potential benefits and side effects of NAC. Overall, NAC seems more effective for adults with TTM than children (70 % vs 40 %). Nevertheless, NAC seems to have benefits for children. Side effects tend to be mild.

The authors’ review included also skin picking disorders and onychophagia. There were 43 patients with skin picking disorders and 26 with onychophagia. 58 % of the patients with skin picking disorders responded to NAC. 100 % of pediatric patients with onychophagia (n=14) and 100 % of adult patients with onychophagia (n=5) responded to NAC.

The authors remind use that NAC is the acetylated precursor of the amino acid L-cysteine. NAC is converted to cysteine in the liver and the majority is used for synthesis of the potent antioxidant glutathione (GSH).

The remaining cysteine crosses the blood–brain barrier and is then converted to cystine. Increased cystine then stimulates exchange of intracellular glutamate by the cystine-glutamate antiporter. Glutamate is a key excitatory central nervous system neurotransmitter and such exchange results in elevated levels of nonsynaptic glutamate.

Increased non-synaptic glutamate binds to glutamate receptors on presynaptic neurons, eliciting an inhibitory effect on synaptic release of glutamate and restoration of extracellular glutamate levels in the nucleus accumbens.

Decline in glutamate levels is hypothesized to block reinstitution of compulsive behaviour and improve impulse control.

Comments and Discussion

This is a very nice study reminding us of the value of NAC in TTM. We need to remember the importance of considering placebo results in all studies of TTM. The placebo effect is huge huge! Studies of pediatric patients and adult patients suggest that anywhere from 20-25 % of patients respond to placebo! We need to keep this in mind at all times.


Nadia Kashetsky et al. Efficacy of N-acetylcysteine in trichotillomania (hair-pulling disorder), skin-picking disorder and onychophagia (compulsive nail-biting). J Eur Acad Dermatol Venereol . 2022 Aug 14.

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