Genetics
Gene Glossary
| Gene | Function | |---|---| | ABCB1 | Helps control how some medications move across the blood-brain barrier.
Written by Sanjida Ahmed, PhD, Cellular and Molecular BiologyChief Operating Officer and Lead Scientist, Personalized Prescribing. Last reviewed October 2, 2026.
| Gene | Function |
|---|---|
| ABCB1 | Helps control how some medications move across the blood-brain barrier. Differences in this gene may influence how much of certain medications reaches the brain. |
| ADRA2A | Makes an important norepinephrine receptor involved in attention, concentration and impulse control. It is particularly relevant to some ADHD medications. |
| BDNF | Helps brain cells grow, adapt and form healthy connections. It is important for learning, memory, stress recovery and neuroplasticity. |
| CES1 | Makes an enzyme that breaks down certain medications, particularly methylphenidate. Differences may affect how quickly the medication is processed. |
| COMT | Helps break down dopamine and norepinephrine, especially in the prefrontal cortex. It can influence attention, motivation and executive function. |
| CYP1A2 | Helps the liver process several medications, including clozapine and olanzapine. Its activity can also be affected by cigarette smoking and other medications. |
| CYP2B6 | Helps process certain medications, including bupropion and some other psychiatric drugs. |
| CYP2C9 | Helps the liver process a variety of medications. Genetic differences can make this enzyme work more slowly or quickly. |
| CYP2C19 | Helps process several antidepressants, including citalopram, escitalopram and sertraline. Genetic differences can affect medication levels and, for some drugs, dosing recommendations. |
| CYP2D6 | One of the most important medication-processing genes in psychiatry. It affects many antidepressants, antipsychotics and ADHD medications. |
| CYP3A4 | Helps process many medications. Its activity can also be strongly affected by other drugs, supplements and foods. |
| CYP3A5 | Works alongside CYP3A4 in processing certain medications. Genetic differences can influence how active this enzyme is. |
| DBH | Helps convert dopamine into norepinephrine. It therefore helps regulate the balance between these two important brain chemicals. |
| DRD2 | Makes the dopamine D2 receptor, an important target of many antipsychotic medications. It is involved in reward, movement, motivation and psychosis-related pathways. |
| DRD3 | Makes the dopamine D3 receptor, which is involved in motivation, reward and emotional functioning. Some antipsychotics act strongly on this receptor. |
| DRD4 | Makes the dopamine D4 receptor, which is involved in attention, behaviour and dopamine signaling. It has been studied in ADHD and psychiatric medication response. |
| DRD4 4R/7R | Different repeating versions of the DRD4 dopamine receptor gene that have been studied in attention, behaviour and ADHD. |
| HTR1A | Makes the serotonin 1A receptor. This receptor helps regulate serotonin release and is also targeted by medications such as buspirone, vilazodone and vortioxetine. |
| HTR1B | Makes a serotonin receptor involved in controlling serotonin release, mood and behaviour. |
| HTR2A | Makes the serotonin 2A receptor. It is involved in mood, anxiety, perception and dopamine regulation and is an important target of many antipsychotic medications. |
| HTR2C | Makes the serotonin 2C receptor. It helps regulate dopamine, appetite, mood and other brain systems. |
| HTR3A | Helps make the serotonin 3 receptor, which is involved in serotonin signaling, nausea, anxiety and communication between brain circuits. |
| HTR3B | Works with HTR3A to form the serotonin 3 receptor and may influence how this receptor responds to serotonin and medications. |
| HTR7 | Makes the serotonin 7 receptor, which is involved in mood, sleep, learning and other serotonin-related brain functions. |
| IDO1 | Helps determine how much tryptophan, a building block for serotonin, is directed toward serotonin production versus other pathways. |
| MAOA | Makes an enzyme that breaks down serotonin, norepinephrine and dopamine. Genetic differences may influence how quickly these brain chemicals are removed. |
| MAOA uVNTR | A repeating section of the MAOA gene that can influence how active the MAO-A enzyme is. |
| MAOB | Makes an enzyme involved mainly in breaking down dopamine and other brain chemicals. |
| SLC6A2 | Makes the norepinephrine transporter (NET), which removes norepinephrine from the space between brain cells. It is an important target of several antidepressant and ADHD medications. |
| SLC6A3 | Makes the dopamine transporter (DAT), which removes dopamine from the space between brain cells. It is especially important in ADHD and stimulant medication response. |
| SLC6A3 9R/10R | Different numbers of repeated DNA sections in the dopamine transporter gene. These may influence dopamine transporter function. |
| SLC6A4 | Makes the serotonin transporter (SERT), which removes serotonin from the space between brain cells. This transporter is the main target of SSRIs. |
| SLC6A4 (5-HTTLPR) | A variation in the SLC6A4 serotonin transporter gene that has been studied for differences in serotonin transporter activity. |
| SLC6A4 (rs25531) | Another variation within SLC6A4 that can further influence how the serotonin transporter gene functions. |
| SLC6A4 (STin2) | A repeating section within SLC6A4 that has been studied for its possible influence on serotonin transporter activity. |
| TH | Helps with the first major step in producing dopamine and norepinephrine. It therefore plays an important role in the body’s ability to make these neurotransmitters. |
| TPH1 | Helps the body produce serotonin from tryptophan. |
| TPH2 | Helps produce serotonin specifically within the brain and nervous system and is important to brain serotonin signaling. |
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