Cannabis & CBD and Your DNA — How Your Genes Affect THC and CBD

What Decode Does

Decode analyzes your CYP2C9, CYP2C19, CYP3A5, and CYP1A2 genotypes and interprets them specifically for cannabis and CBD metabolism. These enzymes influence how fast you clear THC, how you process CBD, and whether smoked cannabis may interact with other medications you take. Decode reports your genotypes and what is known about them — it does not predict whether CBD will give you side effects, because the evidence does not currently support that (see below).

Decode uses the same DNA data already uploaded and analyzed for your other DecodeMyBio results. No new sample or upload is needed.

Genes Analyzed

• CYP2C9 — The primary enzyme forming THC's main active metabolite, 11-OH-THC. In one study of 43 volunteers, people with two copies of the reduced-function *3 variant had roughly 3x higher THC exposure; the *2 variant made no difference.
• CYP2C19 — A primary CBD-metabolizing enzyme alongside CYP3A4, and the main route to the active metabolite 7-OH-CBD.
• CYP3A5 — Reported in a single small study alongside CYP2C19 in connection with CBD-related diarrhea. The contributions of the two genes could not be separated, and the study's authors do not treat this as clinically actionable.
• CYP1A2 — Smoked cannabis (not vaped/edible) induces CYP1A2 through combustion byproducts, affecting caffeine, clozapine, and olanzapine levels.

What You'll See

1. THC Metabolism Profile — Your CYP2C9 diplotype, phenotype, and what it means for THC clearance speed and effect duration.
2. CBD Metabolism Profile — Your CYP2C19 result and how it affects CBD processing and active metabolite production.
3. CYP3A5 + CYP2C19 Genotype Context — Your genotypes for both, with the published research and its limitations (shown only when the combination reported in that study is present). This is context, not a risk prediction.
4. Smoked Cannabis Interactions — CYP1A2 inducibility and which medications are affected by cannabis smoking.
5. Limitations & Disclaimers — Transparent scope boundaries and legal context.

How It Works

1. Upload your DNA data from 23andMe, AncestryDNA, MyHeritage, or FamilyTreeDNA (or use data you've already uploaded).
2. Your existing genotype results for CYP2C9, CYP2C19, CYP3A5, and CYP1A2 are interpreted specifically for cannabis pharmacogenomics.
3. See your results in-app with personalized findings, clinical context, and published research citations.

Key Clinical Evidence

• CYP2C9 and THC: In 43 healthy volunteers given oral THC, CYP2C9*3 homozygotes had a median THC exposure (AUC) about 3-fold higher than *1/*1 individuals, with a trend toward increased sedation; the *2 allele made no difference (Sachse-Seeboth et al., 2009). FDA labeling for dronabinol reflects a 2- to 3-fold exposure difference in people with diminished CYP2C9 function.
• CYP2C19 and CBD: CBD is metabolized primarily by CYP2C19 and CYP3A4, with 7-hydroxylation to the active metabolite 7-OH-CBD predominantly catalyzed by CYP2C19 (FDA Epidiolex label; Jiang et al., 2011). Note that 7-OH-CBD formation tracks CYP2C19 enzyme activity rather than CYP2C19 genotype (Beers et al., 2021).
• CYP3A5 + CYP2C19 and CBD diarrhea: In a secondary analysis of 33 healthy volunteers on prescription-strength CBD, diarrhea occurred in 7 of 18 participants who were both CYP3A5 non-expressers and CYP2C19 intermediate/normal metabolizers, versus 1 of 15 others (p = 0.0463). The authors could not separate the two genes, did not claim causation, and concluded that pharmacogenomic testing may hold questionable utility for predicting these events (Etkins et al., 2026).
• CYP1A2 and Smoking: Plasma levels of clozapine and olanzapine are lower in smokers, mainly through CYP1A2 induction by smoke constituents; stopping tobacco and cannabis smoking has produced clozapine and olanzapine intoxication in reported cases (Zullino et al., 2002).

Learn More

• See a sample — preview what Decode shows before you start
• Cannabis genetics from 23andMe or AncestryDNA data — what your raw data contains and how to use it

Limitations

• Cannabis pharmacogenomics is an evolving field with fewer clinical trials than pharmaceutical PGx. Findings are based on the best available published evidence.
• Decode does not predict whether CBD will cause side effects. The only study linking CYP3A5 and CYP2C19 genotype to CBD-related diarrhea is a secondary analysis of 33 healthy volunteers on prescription-strength doses; it could not separate the two genes, claimed no causal relationship, and its authors concluded that pharmacogenomic testing may hold questionable utility for predicting such events.
• Consumer genotyping chips test a limited set of variants per gene. Rare or novel variants not on the chip will be missed.
• Individual response to cannabis depends on many factors beyond genetics: dose, frequency, consumption method, other substances, and tolerance.
• Decode does not predict subjective experience (euphoria, anxiety, paranoia), cannabis dependence risk, or tolerance effects.

Important Disclaimer

Decode is for educational and informational purposes only. It does not constitute medical advice, diagnosis, or treatment. It does not recommend or endorse cannabis use. Cannabis laws vary by jurisdiction — verify legality in your area before making any decisions. Consult a healthcare provider before making decisions about cannabis or CBD use, especially if you take other medications.

Related

• Pain & Anesthesia — Your CYP enzymes also affect opioid and pain medication response. Learn why codeine and tramadol work differently for different people.
• Psychiatric Medication — CYP2C19 also metabolizes SSRIs and other antidepressants. See how your genetics affect psychiatric medications.
• Celiac & Gluten Screening — Check your HLA-DQ2/DQ8 status from your existing DNA data.

References

1. Sachse-Seeboth C, et al. Interindividual variation in the pharmacokinetics of Δ-9-tetrahydrocannabinol as related to genetic polymorphisms in CYP2C9. Clin Pharmacol Ther. 2009;85(3):273-276. PMID: 19005461.
2. Etkins J, So GC, Lu JBL, et al. Genotype-Specific Safety and Pharmacokinetics of Cannabidiol in Healthy Volunteers. Clin Transl Sci. 2026;19(1):e70455. PMID: 41451876.
3. Correction to “Genotype-Specific Safety and Pharmacokinetics of Cannabidiol in Healthy Volunteers”. Clin Transl Sci. 2026;19(2):e70506. PMID: 41685796.
4. US Food and Drug Administration. EPIDIOLEX (cannabidiol) oral solution — Prescribing Information (Section 12.3: metabolized in the liver and gut primarily by CYP2C19 and CYP3A4). 2018.
5. Jiang R, Yamaori S, Takeda S, Yamamoto I, Watanabe K. Identification of cytochrome P450 enzymes responsible for metabolism of cannabidiol by human liver microsomes. Life Sci. 2011;89(5-6):165-170. PMID: 21704641.
6. Beers JL, Fu D, Jackson KD. Cytochrome P450-Catalyzed Metabolism of Cannabidiol to the Active Metabolite 7-Hydroxy-Cannabidiol. Drug Metab Dispos. 2021;49(10):882-891. PMID: 34330718.
7. Nasrin S, et al. Cannabinoid Metabolites as Inhibitors of Major Hepatic CYP450 Enzymes, with Implications for Cannabis-Drug Interactions. Drug Metab Dispos. 2021;49(12):1070-1080. PMID: 34493602.
8. Zullino DF, Delessert D, Eap CB, Preisig M, Baumann P. Tobacco and cannabis smoking cessation can lead to intoxication with clozapine or olanzapine. Int Clin Psychopharmacol. 2002;17(3):141-143. PMID: 11981356.
9. Dronabinol Therapy and CYP2C9 Genotype. Medical Genetics Summaries. NCBI Bookshelf, NBK564166.