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Supplements for OCD: What NAC and Inositol Trials Show, Including Hair Pulling and Skin Picking

No supplement replaces therapy with exposure and response prevention or an SSRI for OCD. NAC (N-acetylcysteine) added to an SSRI helped a little in some trials of adults and not in others (grade B, mixed). Inositol rests on two tiny trials that disagree (grade C). NAC eased hair pulling and skin picking in one adult trial each (grade C), but not hair pulling in children. Keep taking prescribed medicine.

Published How we grade evidenceEditorial policy

Obsessive-compulsive disorder (OCD) means unwanted, intrusive thoughts (obsessions) and repeated acts or mental rituals (compulsions) done to ease the distress they cause. The treatments with the clearest effects are cognitive behavioural therapy built around exposure and response prevention (ERP), and SSRI antidepressants. Every supplement trial below tested a product on top of usual care or for a few weeks, so none is a replacement. Keep taking any prescribed medicine, and talk to your prescriber before adding anything.

The short version

  • Therapy and SSRIs come first: in 54 trials of adults with OCD (6,652 people), behavioural therapy, cognitive therapy, CBT, clomipramine and SSRIs all beat a drug placebo. Grade A (Skapinakis 2016).
  • NAC (N-acetylcysteine) added to an SSRI: in 6 trials of adults with OCD (195 people), scores fell more than with placebo only at 5 to 8 weeks, and two longer trials found no benefit. Grade B, mixed (Eghdami 2024; Sarris 2015; Costa 2017).
  • Inositol: better than placebo in one 13-person trial, no better as an add-on in 10 people on SSRIs. Grade C (Fux 1996; Fux 1999).
  • NAC for hair pulling (trichotillomania) in adults: 56% much improved against 16% on placebo in one trial of 50 adults. Grade C (Grant 2009). In a trial of 39 children and teens it did no better than placebo (Bloch 2013).
  • NAC for skin picking in adults: in one trial of 66 adults, 47% vs 19% of the 53 who finished were much improved. Grade C (Grant 2016).
  • St John's wort: no better than placebo in 60 people with OCD, and with an SSRI it can cause serotonin syndrome. Grade C for no benefit (Kobak 2005).
OptionWho was testedWhat happenedGrade
NAC added to an SSRI6 trials, 195 adults with OCD, against placeboLower scores at 5 to 8 weeks only; no difference before 5 or after 12 weeksB, mixed
Inositol13 people (alone) and 10 people on SSRIs (add-on), against placeboBetter alone; no better as an add-onC
NAC for hair pulling50 adults, against placebo56% vs 16% much improvedC
NAC for hair pulling39 children and teens, against placebo25% vs 21% responded (no difference)C (no benefit)
NAC for skin picking66 adults, against placebo47% vs 19% much improved (53 who finished)C
St John's wort60 people with OCD, against placeboNo differenceC (no benefit)

What helps OCD most?

Grade A for therapy and SSRIs. Don't stop or swap an SSRI for a supplement. A network analysis of 54 trials (6,652 adults with OCD) found behavioural therapy gave the largest drop on the Y-BOCS, a 0 to 40 symptom scale, against a drug placebo (about 14.5 points, in 11 trials of 287 patients); SSRIs as a group lowered scores by about 3.5 points (37 trials, 3,158 patients) (Skapinakis 2016). For adults, NICE advises CBT that includes ERP (a short course first if OCD is mild), an SSRI or more intensive CBT if it is moderate, and both together if it is severe; for children and teens, CBT with ERP that involves the family comes first (NICE CG31).

Does NAC help OCD?

Grade B, mixed, and only as an add-on to an SSRI. NAC is an amino acid compound studied as a glutamate modulator, acting on a brain signalling chemical. Pooling 6 trials (195 adults with OCD), NAC added to SSRIs lowered total Y-BOCS scores at 5 to 8 weeks, a borderline result (p = 0.05), with no difference under 5 weeks or past 12 weeks and no change in the separate obsession or compulsion scores; the review found no significant difference in reported side effects (Eghdami 2024), though single trials found more stomach pain and heartburn (see Safety). Our condition page does not yet grade NAC for OCD; this B comes from the trials cited here.

Single trials split. In 48 adults whose OCD had not responded to an SSRI-type drug, NAC (up to 2,400 mg daily, over 12 weeks) gave full response in 52.6% against 15% on placebo (Afshar 2012), and 2,000 mg a day added to fluvoxamine lowered scores more than placebo in 44 people with moderate to severe OCD over 10 weeks (Paydary 2016). But 3 g a day for 16 weeks did not beat placebo in 44 adults (responders 20% vs 27%) (Sarris 2015) or in 40 adults with treatment-resistant OCD (scores fell 4.3 vs 3.0 points) (Costa 2017). A review of 17 trials in OCD and related conditions (629 people) found NAC improved overall symptoms, yet no compound it studied raised the number of people who responded (Kishi 2022). Trials in children and teens are few and small; ask your child's psychiatrist. These are trial amounts, not advice; ask your prescriber before adding NAC, especially if you take other medicines.

Does inositol help OCD?

Grade C: small, old trials that disagree. Inositol is a sugar-like compound, a close chemical relative of glucose. In a 1996 crossover trial, 13 people with OCD scored lower on the Y-BOCS while taking 18 g of inositol a day than while on placebo, each taken for 6 weeks (Fux 1996); 18 g is a very large amount that can upset the stomach, so don't try it without your prescriber. Added to an SSRI-type drug, the same 18 g did no better than placebo in 10 people (Fux 1999), and in an open trial of 10 people whose OCD had not responded to these drugs, 7 did not respond (Seedat 1999). Pooling 4 small anxiety-disorder trials (70 people, 2 of them in OCD), inositol made no significant difference to anxiety or obsessive-compulsive symptoms, and stomach upset was slightly more common, a borderline result (Mukai 2014). In hair pulling, a 38-person trial found little to no difference (Hoffman 2021). Our condition page lists the 1996 trial without a grade; we give C because the trials are tiny and disagree.

Does NAC help hair pulling or skin picking?

Grade C in adults, from one trial each. In 50 adults with trichotillomania (45 women), NAC at between 1,200 and 2,400 mg daily for 12 weeks left 56% rated much or very much improved, compared with 16% given placebo; the gains showed after 9 weeks, and no side effects were recorded (Grant 2009). A Cochrane review rated that result moderate certainty and found too little evidence overall to confirm any medicine for hair pulling (Hoffman 2021). In 66 adults with skin-picking disorder, 1,200 to 3,000 mg a day for 12 weeks lowered picking scores more than placebo; of the 53 who finished, 47% were much improved against 19% (Grant 2016). Our condition pages do not yet grade NAC for hair pulling or skin picking; these C grades come from the single trials. These are trial amounts, not advice; ask your prescriber first.

Grade C for no benefit in children and teens. In 39 young people aged 8 to 17 with hair pulling, NAC added to usual care did no better than placebo on any measure, and the authors advised behavioural therapy first (Bloch 2013). For under-18s, ask a clinician.

What we'd skip

  • St John's wort: taken alone by 60 people with OCD, it lowered Y-BOCS scores by 3.43 points against 3.60 on placebo over 12 weeks (Kobak 2005). Don't combine it with an SSRI, an SNRI or clomipramine: the mix can cause serotonin syndrome (see Safety) (sertraline label); see can I take St John's wort with SSRIs?
  • 5-HTP with an SSRI: one 60-person trial added it to fluoxetine and reported lower scores (Yousefzadeh 2020), but 5-HTP adds to serotonin and the combination can cause serotonin syndrome. Don't combine them; any change to your treatment goes through your prescriber. See can I take 5-HTP with SSRIs?
  • Omega-3 EPA: in 11 adults on steady SSRIs, 6 weeks of EPA at 2 g daily was no better than placebo (Fux 2004).
  • Glycine: of 24 adults in the one trial, only 14 could be analysed, mainly because people stopped over its taste or nausea (Greenberg 2009).
  • Valerian, zinc and ashwagandha: each has one small positive trial (31, 23 and 30 people; of the three, only valerian has a grade on our condition page, C) (Pakseresht 2011; Sayyah 2012; Jahanbakhsh 2016): too little to rely on.

Safety and interactions

  • NAC side effects: abdominal pain was more common than on placebo in one OCD trial (60% vs 13%) (Costa 2017), and heartburn in another (Sarris 2015). The label for NAC taken by mouth as a medicine lists nausea, vomiting and other stomach and gut symptoms, and rarely rash or hives; stop it and get help for any allergic reaction (NAC label). In lung-disease trials, an industry-sponsored review found stomach symptoms at oral amounts up to 3,000 mg a day no more common than in control groups (Calverley 2021). No official upper limit has been set; the OCD trials used 2,000 to 3,000 mg a day.
  • Inositol: the OCD trials used 18 g a day, a very large amount; stomach upset was slightly more common than on placebo (Mukai 2014). Inositol is also sold for blood sugar and PCOS; if you take diabetes medicine, see supplements for blood sugar and ask your prescriber. A 1996 letter raised the possibility that inositol triggered mania (Levine 1996); with bipolar disorder, ask your psychiatrist first.
  • Serotonin syndrome: St John's wort and 5-HTP can cause serotonin syndrome, which can be dangerous, when combined with SSRIs, SNRIs or clomipramine; signs include agitation, fever, sweating, a fast heart rate, shaking and muscle twitching. Don't combine them, and get urgent help for these signs. The sertraline label names St John's wort and tryptophan among the products that raise the risk (sertraline label); check any mood supplement with your prescriber, and see supplements and antidepressants.
  • NAC with an SSRI: most NAC trials gave it alongside SSRIs (Eghdami 2024); ask your prescriber before adding it.
  • Pregnancy and breastfeeding: OCD is more common in pregnancy and after birth than in the general population (Russell 2013); the NAC and inositol trials did not test safety in pregnancy or breastfeeding, so don't start them then without your obstetric team, and don't stop an SSRI because you are pregnant; ask your prescriber.
  • Stacks: OCD "support" blends can repeat ingredients; check your stack.

When to see a doctor

  • Now: thoughts of suicide or self-harm, an urge or plan to act on thoughts of harming someone, or feeling unable to stay safe: call or text 988 (US) or your local emergency number. Unwanted, upsetting thoughts of harm that you do not want to act on are a common OCD symptom; tell your doctor or therapist (NICE CG31).
  • Soon: rituals or intrusive thoughts that take up much of your day or get in the way of work, school or relationships; low mood alongside OCD; skin-picking wounds that look infected (spreading redness, heat, pus or fever); OCD that starts suddenly in a child; OCD, hair pulling or skin picking in a child or teen (therapy with ERP that involves the family comes first, not supplements).
  • Before starting a supplement: pregnancy, bipolar disorder, any psychiatric medicine, or age under 18.

Don't stop a prescribed medicine on your own; ask the prescriber or pharmacist. If you are under 18, ask a clinician.

FAQ

Does NAC help OCD? A little, maybe, as an add-on. In 6 trials of adults with OCD (195 people) on SSRIs, NAC lowered scores more than placebo only at 5 to 8 weeks, and two 16-week trials found no benefit (grade B, mixed). It does not replace therapy or an SSRI.

How long does NAC take to work? In the hair-pulling trial in adults, gains first showed after 9 weeks of 12; in the OCD trials pooled, the only difference was at 5 to 8 weeks. Skin-picking and hair-pulling trials ran for 12 weeks.

How much inositol do people take for OCD? The OCD trials in adults used 18 g a day, and results were mixed (grade C). No official upper limit exists; stomach upset was the main side effect. Ask your prescriber first, especially with bipolar disorder.

How much NAC was used in the trials? Adult trials used 1,200 to 3,000 mg a day, for 10 to 16 weeks. No official upper limit exists; stomach pain and heartburn were the main side effects in trials. These are trial amounts, not advice: ask your prescriber first. Children's trials are not a basis for an amount; ask a clinician.

Can I take NAC with sertraline or another SSRI? Most NAC trials in OCD gave it alongside an SSRI. It caused more stomach pain in one trial (60% vs 13%) and heartburn in another, and the oral NAC label lists nausea, vomiting and other gut symptoms. Ask your prescriber before adding it. Don't add St John's wort or 5-HTP to an SSRI: that can cause serotonin syndrome.

Is NAC or inositol better for OCD? No trial has compared them. NAC has more trials (grade B, mixed); inositol rests on two tiny trials that disagree (grade C).

Sources

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