rs324420
A SNP in the FAAH gene on chromosome 1. Its most notable genotype is A;A: significantly increased risk for substance use disorders; possibly higher pain tolerance
- Gene
- FAAH
- Location
- Chr 146,405,089 (GRCh38)
- Highest magnitude
- 2.5Worth knowing
- Tested on
- 23andMe, AncestryDNA, FamilyTreeDNA
- Minor allele frequency
- 25%
Genotypes
As shown in 23andMe and AncestryDNA files.
- A;AMost notableBadsignificantly increased risk for substance use disorders; possibly higher pain tolerance
- A;CNot ratednormal
- C;CGoodnormal
On SNPedia: (A;A), (A;C), (C;C). Magnitude rates how notable a genotype is from 0 to 10, not how risky it is.
Frequency
Share of each genotype in 11 HapMap populations.
- AverageA;A 6% A;C 35% C;C 59%
- European ancestry (Utah)A;A 4% A;C 33% C;C 63%
- Han Chinese (Beijing)A;A 4% A;C 20% C;C 77%
- Japanese (Tokyo)A;A 2% A;C 31% C;C 67%
- Yoruba (Nigeria)A;A 16% A;C 58% C;C 26%
- African ancestry (Southwest US)A;A 5% A;C 49% C;C 46%
- Chinese (Denver)A;A 2% A;C 27% C;C 72%
- Gujarati IndianA;A 6% A;C 27% C;C 67%
- Luhya (Kenya)A;A 12% A;C 41% C;C 47%
- Mexican ancestry (Los Angeles)A;A 3% A;C 40% C;C 57%
- Maasai (Kenya)A;A 7% A;C 39% C;C 55%
- TuscanA;A 3% A;C 25% C;C 73%
Related
Conditions, medicines and genes
Notes
From SNPedia
Show notes, about 350 words
rs324420, also known as c.385C>A or Pro129Thr, is a SNP in the fatty acid amide hydrolase FAAH gene, which has shown associations with some substance use disorders. rs324420(C) encodes the more common Pro, while the (A) allele encodes the Thr. Among 80 individuals with drug abuse or alcoholism and over 1,000 controls, the odds ratio for risk of problem drug or alcohol use among rs324420(A;A) individuals was 4.5 (CI: 2.2 - 8.4); the odds ratio for risk of street drug use was 2.2 (CI: 1.3–3.7); and the odds ratio for risk of combined street drug use and problem drug/alcohol use was 4.9 (CI: 2.5–9.7) When this study was pooled with the results of another study of 249 subjects with documented multiple different drug addictions compared to drug free individuals of the same ethnic backgrounds, the results were consistent and even more significant (p = 0.00003). Risk for drug dependence (and drug abuse was associated with rs324420(A;A) homozygotes. In a study of 40 daily marijuana users who abstained for 24 h and were then presented with a cue-elicited craving paradigm, followed by smoking a marijuana cigarette, rs324420(A) was significantly associated with changes in withdrawal after abstinence and with happiness after smoking marijuana, but was not associated with changes in heart rate after smoking or with changes in craving or other acute effects. This variant has also been associated with pain insensitivity. In a 2016 study, ~1000 women undergoing surgery for breast cancer were tested for cold and heat pain sensitivity; rs324420(A;A) individuals reported significantly lower cold pain sensitivity and less need for postoperative analgesia. The rs324420(A;C) genotype was also seen in a woman with unusually high pain tolerance, along with a ~8kb heterozygous microdeletion of the adjacent FAAH pseudogene. And from a different perspective, a 2016 study published in the Journal of Happiness Studies found "a strong correlation between a nation's happiness and the presence of the (rs324420) A allele in the fatty acid amide hydrolase (FAAH) gene". (news mention; ) * See also OMIM
Source and license
Adapted from rs324420 on SNPedia, using a snapshot taken October 16, 2026. SNPedia content is shared under CC BY-NC-SA 3.0 US, and this page is shared under the same license.
SNPedia is a community-edited wiki. Its entries can be incomplete, out of date or wrong, and nothing here is a diagnosis or medical advice. Magnitude is a community rating of how interesting a genotype is, not a risk score.