What you carry at this position in your DNA and what research says about it.
Caffeine and Drug Response: 5/10 evidence, 6 publications.
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Sample genotype (not yours): T/T
Typical Caffeine Metabolism and Better Antidepressant Response
Carrying two copies of the T allele is associated with standard caffeine clearance and a higher likelihood of remission when taking paroxetine. It also avoids the elevated risks of metabolic syndrome and slower drug processing linked to the C allele.
What this genotype means: Standard caffeine clearance; Higher likelihood of paroxetine remission; Typical risk of type 2 diabetes.
Sample genotype (not yours): C/C
Lower Parkinson's Risk with Slower Drug Metabolism
Carrying two copies of the C allele is associated with a reduced risk of Parkinson's disease in coffee drinkers but slower clearance of certain medications. It is also linked to a typical response to paroxetine and a slightly higher risk of type 2 diabetes.
What this genotype means: Reduced risk of Parkinson's disease with coffee; Slower deferasirox clearance; Slightly increased risk of type 2 diabetes.
Sample genotype (not yours): T/C
Enhanced Antidepressant Response with Slower Drug Clearance
Carrying one copy of the C allele is linked to a better response to paroxetine but also slower metabolism of certain medications. It may also slightly increase the risk of type 2 diabetes when combined with regular coffee consumption.
What this genotype means: Higher likelihood of paroxetine remission; Slower deferasirox clearance; Slightly increased risk of type 2 diabetes.
Gene function and biological role
Gene Function: The CYP1A2 gene encodes cytochrome P450 1A2, a major liver enzyme responsible for metabolizing a wide range of foreign compounds. This enzyme plays a central role in breaking down caffeine, melatonin, and several clinical medications [1]. It is also involved in the metabolic activation of procarcinogens, which can influence cancer susceptibility [2]. Variations in this gene can significantly alter enzyme activity, leading to wide differences in how people process everyday stimulants and therapeutic drugs [3].
Variant Impact: The rs2470890 variant is a synonymous single-nucleotide change located in the coding region of the CYP1A2 gene. Although it does not change the resulting amino acid sequence, it is highly linked to alterations in enzyme expression and drug clearance [1]. This genetic marker has been studied for its role in modulating the therapeutic effects of antidepressants like paroxetine [3]. It also influences the clearance rate of iron-chelating therapies and interacts with caffeine intake to affect metabolic health [4] [5].
Key Insight: This variant acts as a metabolic modifier where the same allele that protects against Parkinson's disease under caffeine exposure also increases the risk of type 2 diabetes and slows down the clearance of specific prescription medications.
Location: CYP1A2. Chromosome 15 · 15q24.1 · 74.8 Mb
Estimated prevalence by population
Global 23.9%; European 41.8%; African 1.3%; East Asian 2.5%; South Asian 3.7%; Americas 12.2%; Ashkenazi 30.1%; Finnish 31.2%; Middle Eastern 28.9%; Amish 20.8%.
Estimated TT genotype frequency.
Global 37.9%; European 45.7%; African 20.2%; East Asian 26.4%; South Asian 31.0%; Americas 45.5%; Ashkenazi 49.5%; Finnish 49.3%; Middle Eastern 49.7%; Amish 49.6%.
Estimated TC genotype frequency.
Global 38.2%; European 12.5%; African 78.5%; East Asian 71.1%; South Asian 65.3%; Americas 42.3%; Ashkenazi 20.3%; Finnish 19.4%; Middle Eastern 21.4%; Amish 29.6%.
Estimated CC genotype frequency.
Showing effects for T/T genotype
Neurology & Mental Health
Neurodegenerative Diseases
Parkinson's Disease. Evidence: 5/10. Source: PMID 21281405. Typical Risk.
Pharmacogenomics
Antidepressant & Psychiatric Drug Response
Antidepressant Response. Evidence: 5/10. Source: PMID 21121774. Stronger Response.
Drug Metabolism Enzyme Activity
Deferasirox Metabolism. Evidence: 5/10. Source: PMID 25348619. Typical Metabolism.
Cardiovascular & Metabolic
Diabetes & Glycemic Traits
Type 2 Diabetes. Evidence: 3/10. Source: PMID 26588584. Typical Risk.
Cancer & Oncology
Lung Cancer
Lung Cancer. Evidence: 3/10. Source: PMID 25081684. Typical Risk.
Showing effects for C/C genotype
Parkinson's Disease. Evidence: 5/10. Source: PMID 21281405. Lower Risk.
Antidepressant Response. Evidence: 5/10. Source: PMID 21121774. Typical Response.
Deferasirox Metabolism. Evidence: 5/10. Source: PMID 25348619. Slower Metabolism.
Type 2 Diabetes. Evidence: 3/10. Source: PMID 26588584. Increased Risk.
Showing effects for T/C genotype
What this genotype means for the people who carry it
Sample genotype: TT (Homozygous)
Having the T/T genotype means the liver processes caffeine and certain medications at a standard, typical rate [1]. Clinical studies indicate that individuals with this genotype experience a significantly higher rate of remission when treated with the antidepressant paroxetine [2]. Furthermore, this genotype does not carry the increased risk of type 2 diabetes associated with caffeine intake seen in C allele carriers [3]. It also maintains normal clearance of the iron-overload medication deferasirox [4]. While it does not provide the caffeine-mediated reduction in Parkinson's disease risk seen with the C/C genotype, it represents a balanced metabolic profile [1]. No significant association with lung cancer risk has been established for this genotype [5].
Standard caffeine clearance; Higher likelihood of paroxetine remission; Typical risk of type 2 diabetes.
Sample genotype: CC (Homozygous)
This genotype is notable for its protective interaction with caffeine. Individuals carrying two copies of the C allele who regularly consume coffee exhibit a significantly decreased risk of developing Parkinson's disease [1]. On the other hand, this genetic profile is associated with a standard, rather than enhanced, response to the antidepressant paroxetine [2]. It also leads to slower metabolism of the iron-overload treatment deferasirox, potentially increasing the risk of side effects due to drug accumulation [3]. Furthermore, the C/C genotype is linked to a slightly higher baseline risk of type 2 diabetes, which may be further influenced by daily caffeine intake [4]. Meta-analyses show no significant correlation between this genotype and lung cancer susceptibility [5].
Reduced risk of Parkinson's disease with coffee; Slower deferasirox clearance; Slightly increased risk of type 2 diabetes.
Sample genotype: TC (Heterozygous)
This heterozygous genotype presents a mix of metabolic advantages and potential drug sensitivities. Research shows that carrying one T allele preserves the increased likelihood of achieving remission when using the antidepressant paroxetine [1]. However, the presence of the C allele is associated with slower clearance of the iron-chelating drug deferasirox, which can lead to higher drug levels in the body [2]. Additionally, this genotype is linked to a slightly elevated risk of type 2 diabetes, an effect that can be amplified by regular caffeine consumption [3]. Standard caffeine clearance remains largely typical, but individuals may want to monitor their response to stimulants [4]. No elevated risk of lung cancer has been associated with this genetic pattern [5].
Higher likelihood of paroxetine remission; Slower deferasirox clearance; Slightly increased risk of type 2 diabetes.
Variants with shared genetic architecture
rs762551 · CYP1A2 Gene · Chr 15 · Caffeine Metabolism
rs2069514 · CYP1A2 Gene · Chr 15 · Caffeine and Drug Metabolism
rs2472304 · CYP1A2 Gene · Chr 15 · Caffeine and Parkinson's
Coffee, ADORA2A, and CYP1A2: the caffeine connection in Parkinson's disease.
Four polymorphisms in the cytochrome P450 1A2 (CYP1A2) gene and lung cancer risk: a meta-analysis.
Influence of single-nucleotide polymorphisms on deferasirox C trough levels and effectiveness.
Caffeine Impact on Metabolic Syndrome Components Is Modulated by a CYP1A2 Variant.
Content updated August 2026.
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