N-acetylcysteine, a glutamate modulator, in the treatment of trichotillomania: a double-blind, placebo-controlled study.
For hair-pulling or skin-picking, how does NAC compare with habit-reversal therapy, which has evidence in both adults and children?
Reasonable evidence with real limitations. how we score evidence
Caveat on this rating: One trial, 50 people, one site, and a very large effect — the combination that most often fails to replicate, and in this case did fail to replicate in children four years later. No funding or disclosure statement could be read (the journal page returned HTTP 403 on 2026-08-18), so funding is UNKNOWN, conflicts false, and independence left null.
NAC sits in an unusual place.
50 adults with trichotillomania (45 women, 5 men, mean age 34) received NAC 1,200-2,400 mg/day or placebo for 12 weeks. NAC produced significantly greater reductions in hair-pulling on the Massachusetts General Hospital Hair Pulling Scale (P<.001) and the Psychiatric Institute Trichotillomania Scale (P=.001), with 56% "much or very much improved" versus 16% on placebo — a 40-percentage-point absolute difference. Benefit did not appear until about week 9. No adverse events were reported in the NAC group. This single 50-person trial is the origin of NAC's reputation for compulsive behaviours; read it together with the failed replication below.
Worth asking
For hair-pulling or skin-picking, how does NAC compare with habit-reversal therapy, which has evidence in both adults and children?
Source
N-acetylcysteine, a glutamate modulator, in the treatment of trichotillomania: a double-blind, placebo-controlled study. — Grant JE, Odlaug BL, Kim SW. (2009)
Top-tier peer-reviewed journal
Read the source: https://doi.org/10.1001/archgenpsychiatry.2009.60
DOI: 10.1001/archgenpsychiatry.2009.60
How this was scored
- Study design
- Randomised controlled trial
- Funding
- Funding not disclosed
- Published in
- Top-tier peer-reviewed journal
- Sample size
- 50
- Preregistered
- Yes
- Conflicts disclosed
- No
- Independent of proponent
- not recorded
- Retracted
- No
Read the full scoring rubric, including what it can't tell you.
Published August 19, 2026.
Questions
How strong is the evidence behind this?
Resolv rates this source "moderate evidence". Reasonable evidence with real limitations. It scores 66 out of 100 on our published rubric. One caveat travels with that badge: One trial, 50 people, one site, and a very large effect — the combination that most often fails to replicate, and in this case did fail to replicate in children four years later. No funding or disclosure statement could be read (the journal page returned HTTP 403 on 2026-08-18), so funding is UNKNOWN, conflicts false, and independence left null. The score is calculated from recorded facts about the source — study design, funding, publication venue, sample size, preregistration — not typed in by an editor.
What is the source for this?
N-acetylcysteine, a glutamate modulator, in the treatment of trichotillomania: a double-blind, placebo-controlled study. — Grant JE, Odlaug BL, Kim SW. (2009). Published in: Top-tier peer-reviewed journal. DOI: 10.1001/archgenpsychiatry.2009.60. The full source is linked on this page so you can read it yourself.
Who paid for this research, and does that matter?
Study design: Randomised controlled trial. Funding: Funding not disclosed. Independence from the proponent is not recorded. Industry sponsorship is one of the most reliably measured biases in medicine, which is why funding carries real weight in the score rather than sitting in a footnote.
Is nac, n-acetylcysteine, n-acetyl-l-cysteine, acetylcysteine, acetadote, mucomyst FDA approved for this use?
No. Its current status is: Not FDA-evaluated for this use. NAC sits in an unusual place.
Is this medical advice?
This is information to bring to your prescriber, not medical advice and not a reason to change anything on your own. Nothing here is an instruction to stop or reduce a medication. If you are in crisis, call or text 988.
This is information to bring to your prescriber, not medical advice and not a reason to change anything on your own. Nothing here is an instruction to stop or reduce a medication. If you are in crisis, call or text 988.