Glycine for OCD: Not Recommended as Standard Treatment
Glycine is not recommended as a standard treatment for OCD and should not replace evidence-based first-line therapies (CBT with ERP or SSRIs), though it may be considered as an experimental augmentation strategy in highly refractory cases after exhausting all established treatment options. 1, 2
Why Glycine Is Not Standard Treatment
The established treatment algorithm for OCD does not include glycine at any stage 3, 1, 2:
- First-line treatment consists of CBT with exposure and response prevention (ERP) or SSRIs, with CBT showing superior efficacy (number needed to treat of 3 versus 5 for SSRIs) 1, 2
- Second-line options include optimizing SSRI dosing, switching SSRIs, adding clomipramine, or augmenting with atypical antipsychotics 2, 4
- Third-line strategies for treatment-resistant OCD include glutamatergic agents like N-acetylcysteine (NAC), which has the strongest evidence base among glutamatergic medications, with 3 out of 5 RCTs showing superiority to placebo 4
- Fourth-line interventions include intensive CBT protocols, neuromodulation (FDA-approved deep rTMS), or deep brain stimulation for extremely refractory cases 5, 2, 4
Limited Evidence for Glycine
The evidence supporting glycine for OCD is extremely weak 6, 7:
- Only one single case report exists describing glycine treatment over 5 years in a patient with OCD and body dysmorphic disorder who had failed multiple standard treatments 7
- A systematic review of complementary treatments found "tentative evidentiary support" for glycine (effect size d=1.10) but rated this as coming from "methodologically weak studies" that were "un-replicated and commonly used small samples," precluding "firm confidence in the strength of clinical effect" 6
- The case report involved a patient with suspected NMDA receptor dysfunction following streptococcal infections, representing a highly atypical presentation not generalizable to typical OCD 7
Superior Glutamatergic Alternative
If you are considering glutamatergic modulation for treatment-resistant OCD, N-acetylcysteine (NAC) should be chosen instead of glycine 4:
- NAC has the largest evidence base among glutamatergic agents, with multiple RCTs demonstrating efficacy at doses of 2000-3000 mg/day for 12 weeks or longer 4
- NAC showed a robust effect size (d=1.31) in trichotillomania, a related compulsive disorder 6
- NAC is specifically highlighted in treatment guidelines as having superior evidence compared to other glutamatergic agents 4
Related Agent: Sarcosine
Sarcosine (a glycine transporter-1 antagonist that increases synaptic glycine availability) showed more promise than glycine itself in a small open-label trial 8:
- In 25 OCD patients, sarcosine 500-2000 mg/day produced a mean 19.8% reduction in Y-BOCS scores over 10 weeks, with 32% achieving response (>35% reduction) 8
- Drug-naive patients showed more profound improvement than previously treated patients 8
- However, this was an uncontrolled, open-label study without placebo comparison, limiting conclusions 8
Clinical Bottom Line
Do not use glycine as a treatment for OCD in routine clinical practice. Follow the evidence-based treatment algorithm: start with CBT with ERP and/or SSRIs, escalate through established second-line options (SSRI optimization, clomipramine, antipsychotic augmentation), then consider NAC as the preferred glutamatergic agent before exploring experimental options 1, 2, 4. Glycine lacks the rigorous evidence base required to recommend it over proven treatments, and using it prematurely could delay access to effective therapies 3, 6.