Obsessive-compulsive disorder (OCD) is one of the most stubborn mental health conditions to treat. If you or someone you know has OCD, you’re probably already aware that standard treatments don’t work perfectly for everyone. The first-line approaches are serotonergic antidepressants (particularly SSRIs) and a specific form of cognitive behavioural therapy called exposure and response prevention (ERP). These treatments have good evidence behind them. But here’s the uncomfortable reality: roughly 40-60% of patients don’t respond adequately to SSRIs alone [1].

That’s a lot of people left searching for additional help. Which brings us to adjuvant therapies—treatments used alongside standard care that might improve outcomes for those who haven’t found relief from conventional approaches.

I should be clear about what follows: none of these adjuvant therapies are replacements for evidence-based treatment. They’re potential additions that may help some people. The evidence for each varies considerably, and honest assessment of what the research actually shows is more useful than false hope.

What exactly is OCD?

Before diving into adjuvant therapies, it helps to understand what we’re dealing with. OCD is a heterogeneous psychiatric disorder, meaning it presents differently in different people. The lifetime prevalence sits somewhere between 1% and 3% of the general population [2].

The core features are:

Obsessions: Recurrent, intrusive thoughts, images, or urges that cause significant anxiety or distress. The person recognises these as products of their own mind (they’re not hearing external voices), yet cannot simply dismiss them. Common themes include contamination fears, doubts about whether you’ve done something properly, need for symmetry or order, and disturbing aggressive or sexual thoughts that conflict with the person’s values.

Compulsions: Repetitive behaviours or mental acts performed to neutralise the anxiety from obsessions. Hand washing, checking locks, counting, arranging objects, seeking reassurance, mentally reviewing past events. The compulsions provide temporary relief but ultimately reinforce the cycle.

OCD differs from related conditions. It’s not the same as obsessive-compulsive personality disorder (OCPD), which involves perfectionism and need for control but lacks the ego-dystonic intrusive thoughts. It shares features with body dysmorphic disorder and trichotillomania (hair-pulling), sometimes grouped under “obsessive-compulsive spectrum disorders.”

Left untreated, OCD tends to become chronic and progressively disabling. It can wreck relationships and make holding down a job nearly impossible [3]. Getting effective treatment matters enormously.

Standard treatment approaches

The evidence-based treatments for OCD are:

Selective serotonin reuptake inhibitors (SSRIs): Fluoxetine, sertraline, fluvoxamine, paroxetine, and citalopram all have evidence in OCD. Clomipramine, an older tricyclic antidepressant with strong serotonergic action, is also effective but typically reserved as second-line due to its side effect profile.
Exposure and response prevention (ERP): This specific form of CBT involves deliberately exposing yourself to anxiety-provoking triggers while resisting the urge to perform compulsions. It sounds brutal, and honestly, it is difficult. But it works. The principle is that anxiety naturally decreases if you stay with a trigger long enough without performing the compulsion—a process called habituation.
Combination therapy: SSRIs plus ERP together often produce better results than either alone.

Some patients achieve full remission with behavioural therapy alone and never require long-term medication. Others need ongoing pharmacological support. There’s no one-size-fits-all answer.

For severe, treatment-resistant cases, options include augmentation with antipsychotics, higher-dose SSRIs, or, very rarely, neurosurgical interventions. But what about the space between “standard treatment alone” and “treatment-resistant”? That’s where adjuvant therapies come in.

Adjuvant therapy 1: N-acetylcysteine (NAC)

N-acetylcysteine is an acetylated form of the amino acid L-cysteine. Your body uses it to produce glutathione, an important antioxidant. NAC has been a prescription medication for decades, used primarily as a mucolytic (breaking up mucus in respiratory conditions) and as the antidote for paracetamol overdose.

More recently, psychiatrists have become interested in NAC for various conditions including OCD, addiction, depression, and autism spectrum disorders. The rationale involves glutamate, the brain’s primary excitatory neurotransmitter. Glutamate signalling dysfunction appears to play a role in OCD, and NAC modulates glutamate through its effects on the cystine-glutamate antiporter [4].

What does the evidence show?

A systematic review examined 5 randomised placebo-controlled trials of NAC in OCD, plus several case reports and case series [5]. The overall impression was positive—NAC as an add-on to standard treatment appeared beneficial.

However, I need to be honest about the limitations. The included trials were small, the methodological quality varied, and there was significant heterogeneity in how OCD was measured. This is preliminary evidence, not a settled conclusion.

One well-designed double-blind trial gave 48 patients with OCD either NAC (2,400 mg daily) or placebo for 12 weeks, all while continuing their SSRI treatment [6]. The NAC group showed greater improvement on the Yale-Brown Obsessive Compulsive Scale (Y-BOCS), the standard measurement tool for OCD severity. The effect size was moderate.

Practical considerations: NAC has a good safety profile. Common side effects include gastrointestinal upset, and it has a distinctive sulfurous smell. Typical doses in the research range from 1,200 to 3,000 mg daily. It’s relatively inexpensive and widely available.

My assessment: NAC shows promise as an adjuvant therapy. The evidence isn’t definitive, but the risk-benefit ratio seems favourable for someone already on standard treatment who wants to try something additional. I wouldn’t expect dramatic results, but modest improvement is plausible.

Adjuvant therapy 2: Ashwagandha (Withania somnifera)

Ashwagandha, also called Indian ginseng or winter cherry, is a plant used in Ayurvedic medicine for centuries. It’s classified as an adaptogen—substances claimed to help the body adapt to stress and normalise physiological function.

Researchers think it works by modulating the HPA axis (the body’s stress response system) and possibly by enhancing serotonin production. It also has some GABA-like activity. All of this is relevant to anxiety, and potentially to OCD.

What does the evidence show?

One double-blind controlled study looked at 30 OCD patients already taking SSRIs [7]. Half received ashwagandha extract alongside their medication; half received placebo. After six weeks, the ashwagandha group showed significantly greater improvement on the Y-BOCS compared to the placebo group.

That’s a positive finding. But thirty patients over six weeks? This is a single small trial. It’s suggestive but nowhere near conclusive.

The proposed mechanism—that ashwagandha enhances serotonin synthesis and regulates synaptic receptors—makes biological sense. If SSRIs work by increasing serotonin availability, something that helps with serotonin production could theoretically be synergistic.

Ashwagandha has better evidence for generalised anxiety than for OCD specifically. A 2014 systematic review found five trials showing significant improvement in anxiety scores [8]. Since anxiety and OCD overlap considerably (OCD was classified under anxiety disorders until DSM-5), this indirect evidence isn’t irrelevant.

Practical considerations: Ashwagandha appears generally safe. Gastrointestinal upset is the most common side effect. The research typically uses standardised root extracts at doses of 300-600 mg daily. However, ashwagandha can interact with thyroid medications and may not be suitable for people with autoimmune thyroid conditions.

My assessment: There’s a reasonable theoretical basis and one positive small trial specifically for OCD. The general anxiety evidence provides additional support. It’s not unreasonable to try as an adjuvant, but manage expectations accordingly.

Adjuvant therapy 3: Valerian (Valeriana officinalis)

Valerian root has been used in European traditional medicine for centuries, primarily for sleep and anxiety. The plant’s rhizome contains essential oils, valerenic acid (which interacts with GABA receptors), and various amino acids including GABA itself.

The connection to OCD isn’t immediately obvious, but consider: anxiety is a core feature of OCD, and compounds that modulate GABA signalling can reduce anxiety. Benzodiazepines work primarily through GABA-A receptor enhancement, and while nobody suggests benzodiazepines as an OCD treatment (they don’t address the underlying pathology), there’s logic in exploring other GABA-modulating compounds.

What does the evidence show?

One randomised, double-blind, placebo-controlled trial tested valerian root extract in 31 OCD patients [9]. Participants took 765 mg of valerian extract daily (or placebo) for eight weeks. The valerian group showed significantly greater improvement on the Y-BOCS compared to placebo.

Again, thirty-one patients is a small sample. This is hypothesis-generating, not definitive proof. But the trial was reasonably well designed (randomised, double-blind, placebo-controlled) and they used the Y-BOCS, which is the gold standard for measuring OCD severity.

The mechanism is likely related to valerian’s effects on GABA-A receptors. Valerenic acid has been shown in laboratory studies to enhance GABA receptor function, though the exact clinical relevance remains uncertain.

Practical considerations: Valerian has a good safety record. Side effects are mild and uncommon—mostly gastrointestinal. One practical issue: valerian smells terrible. Most people prefer capsules over loose powder or tea for this reason.

One thing to watch: valerian can enhance the effects of other sedatives, including alcohol. The NHS notes that valerian is commonly used for sleep and anxiety but advises that more research is needed [10].

My assessment: One positive small trial. The GABA-modulating mechanism is plausible. Valerian is safe, inexpensive, and widely available. As adjuvant therapies go, it’s a reasonable option to try alongside standard treatment.

Adjuvant therapy 4: Aerobic exercise

This is the easiest one to start, requires no supplements, and has the broadest evidence base for mental health generally. Exercise isn’t a supplement you buy; it’s something you do.

The global problem of insufficient physical activity is well documented. About two-thirds of adults fail to meet minimum exercise recommendations. The consequences go well beyond cardiovascular health; sedentary behaviour is associated with higher rates of depression and anxiety [11].

What does the evidence show?

A randomised controlled trial looked at 55 patients with treatment-resistant OCD—people who hadn’t responded adequately to standard treatment [12]. Participants were assigned to either 12 weeks of moderate aerobic exercise (supervised sessions three times weekly) or a control condition (health education classes).

The results were notable. The exercise group showed significantly greater improvement in OCD symptoms. They also reported increased positive affect and reduced anxiety. Importantly, these were patients who had already tried and failed standard approaches—a population where any additional improvement is valuable.

Why might exercise help OCD? A few plausible explanations: exercise increases serotonin and dopamine release, which affects mood and anxiety. It also increases BDNF (brain-derived neurotrophic factor), which supports neuroplasticity and might help the brain break out of entrenched patterns. Then there’s the stress angle: chronic stress throws cortisol regulation out of whack, and exercise helps normalise it. And honestly, there’s something to be said for the simple psychological benefits. Going for a run gives you a break from the rumination, plus the satisfaction of having done something.

Practical considerations: What counts as “aerobic exercise”? The OCD trial used moderate-intensity activity (brisk walking, jogging, cycling) at about 70% of maximum heart rate, for 30-40 minutes, three times weekly.

You don’t need a gym membership or expensive equipment. Walking briskly for 30 minutes is a start. The key is consistency over time.

Exercise is virtually free, has minimal side effects (muscle soreness, basically), and the benefits extend well beyond mental health. Your heart, bones, and metabolism all benefit too.

My assessment: Of the four adjuvant therapies discussed, aerobic exercise has the strongest overall evidence base and the best safety profile. One good trial specifically in treatment-resistant OCD, plus decades of research on exercise for anxiety and depression generally. The only barrier is actually doing it.

What about other supplements?

You might wonder about other substances sometimes mentioned for OCD:

GABA supplements: Despite GABA’s role as the main inhibitory neurotransmitter, there’s genuine doubt about whether orally taken GABA crosses the blood-brain barrier. The research in OCD specifically is absent.

St. John’s wort: Has evidence for mild-to-moderate depression but not specifically for OCD. Also, it has serious drug interactions with many medications, including some SSRIs.

Myo-inositol: One study suggested benefit, but subsequent trials failed to replicate.

Kava: Evidence for generalised anxiety, but liver toxicity concerns limit recommendations.

The four therapies covered in this article (NAC, ashwagandha, valerian, and aerobic exercise) have the most relevant preliminary evidence specifically in OCD.

Important caveats

A few things bear repeating:

These are adjuvant therapies. They’re meant to be added to standard treatment, not to replace it. If you have OCD and aren’t already working with a mental health professional, that’s the first step.

The evidence is preliminary. Small trials are not the same as large, replicated studies. What looks promising in 30 patients might disappear in 300.

Individual variation is enormous. Something that helps one person may do nothing for another. This is true of psychiatric treatments generally.

Talk to your doctor before adding supplements. NAC, ashwagandha, and valerian all have potential interactions, particularly with sedatives and psychiatric medications.

Don’t stop prescribed medications without medical supervision. Stopping SSRIs abruptly can cause discontinuation syndrome. Any changes to your treatment should be managed with your prescriber.

References

Pallanti S, Quercioli L. Treatment-refractory obsessive-compulsive disorder: methodological issues, operational definitions and therapeutic lines. Prog Neuropsychopharmacol Biol Psychiatry. 2006;30(3):400-412.
Ruscio AM, Stein DJ, Chiu WT, Kessler RC. The epidemiology of obsessive-compulsive disorder in the National Comorbidity Survey Replication. Mol Psychiatry. 2010;15(1):53-63.
NICE. Obsessive-compulsive disorder and body dysmorphic disorder: treatment. Clinical guideline [CG31]. 2005 (updated 2020). Available from: https://www.nice.org.uk/guidance/cg31
Oliver G, Dean O, Camfield D, et al. N-acetyl cysteine in the treatment of obsessive compulsive and related disorders: a systematic review. Clin Psychopharmacol Neurosci. 2015;13(1):12-24.
Rodrigues-Barata AR, Teixeira AL, Louzã MR. N-acetylcysteine as a novel treatment for obsessive-compulsive disorder: a systematic review of the clinical evidence. Curr Drug Targets. 2016;17(8):971-976.
Afshar H, Roohafza H, Mohammad-Beigi H, et al. N-acetylcysteine add-on treatment in refractory obsessive-compulsive disorder: a randomized, double-blind, placebo-controlled trial. J Clin Psychopharmacol. 2012;32(6):797-803.
Jahanbakhsh SP, Manteghi AA, Emami SA, et al. Evaluation of the efficacy of Withania somnifera (Ashwagandha) root extract in patients with obsessive-compulsive disorder: A randomized double-blind placebo-controlled trial. Complement Ther Med. 2016;27:25-29.
Pratte MA, Nanavati KB, Young V, Morley CP. An alternative treatment for anxiety: a systematic review of human trial results reported for the Ayurvedic herb ashwagandha (Withania somnifera). J Altern Complement Med. 2014;20(12):901-908.
Pakseresht S, Boostani H, Sayyah M. Extract of valerian root (Valeriana officinalis L.) vs. placebo in treatment of obsessive-compulsive disorder: a randomized double-blind study. J Complement Integr Med. 2011;8.
NHS. Herbal medicines. Available from: https://www.nhs.uk/conditions/herbal-medicines/
World Health Organization. Global recommendations on physical activity for health. Geneva: WHO; 2010.
Abrantes AM, Brown RA, Strong DR, et al. A pilot randomized controlled trial of aerobic exercise as an adjunct to OCD treatment. Gen Hosp Psychiatry. 2017;49:51-55.

What exactly is OCD?

Standard treatment approaches

Adjuvant therapy 1: N-acetylcysteine (NAC)

Adjuvant therapy 2: Ashwagandha (Withania somnifera)

Adjuvant therapy 3: Valerian (Valeriana officinalis)

Adjuvant therapy 4: Aerobic exercise

What about other supplements?

Important caveats

References

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