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Pharmacogenetics helps to find right psychiatric medication and dose

Ruslan Dorfman, PhD, MBA30 Oct 2026

Many people live with mental health conditions, and finding the right medication can take time. Commonly prescribed antidepressants such as SSRIs help many people with anxiety and depression, but they don't suit everyone. Some people can't tolerate the side effects of antidepressants or don't find them effective. Antipsychotics and mood stabilizers are important treatments for bipolar disorder, schizophrenia and, in some cases, depression, anxiety and obsessive-compulsive disorder. Yet the stigma around psychiatric medications and the fear of side effects lead many people to avoid treatment. Working closely with a mental health professional, and using your DNA to guide medication choice and dose, can help you find a treatment plan that works for you.

This article focuses on antipsychotics, mood stabilizers and ADHD medications. For antidepressants, read Can genetic testing help me to choose psychiatric medications?

Which conditions can antipsychotic medications help?

Second-generation antipsychotics are approved for schizophrenia and bipolar disorder, and some are also used for other conditions. A 2023 review of 181 placebo-controlled trials in more than 65,000 people compared how well these medications worked for conditions other than schizophrenia. The medications that ranked highest were:

Aripiprazole (Abilify): bipolar mania and Tourette's syndrome
Olanzapine (Zyprexa): bipolar depression and post-traumatic stress disorder (PTSD)
Lurasidone (Latuda): depression
Quetiapine (Seroquel): anxiety and sleep problems
Risperidone (Risperdal): obsessive-compulsive disorder (OCD)

These rankings compare each medication with a placebo, not with each other, and side effects differed between medications. Some of these uses are off-label. If several antidepressants haven't helped, your doctor may consider adding an antipsychotic or a mood stabilizer. The right choice depends on your diagnosis, symptoms, other medications and how well you tolerate side effects.

How can I find a psychiatric medication that is safe and effective for me?

Your psychiatrist will consider treatment options that best match your diagnosis and symptoms. Because of concerns about side effects, many doctors use a "start low, go slow" approach. This is safe, but it can lengthen the time it takes to find a dose that relieves symptoms. Most psychiatric medications are broken down by liver enzymes, and genes such as CYP2D6 and CYP3A4 affect how active these enzymes are. Pharmacogenetic testing shows whether your body is likely to clear a medication too slowly, which raises the risk of side effects, or too quickly, which can make it less effective. Your doctor can use this information to choose a medication and adjust its dose. For some medications, measuring drug levels in the blood (therapeutic drug monitoring) can then fine-tune the dose.

What do guidelines say about genes and psychiatric medications?

The Dutch Pharmacogenetics Working Group (DPWG) published an evidence-based guideline for antipsychotics in 2023. Drug labels from Health Canada and the FDA, and guidelines from the Clinical Pharmacogenetics Implementation Consortium (CPIC), cover other psychiatric medications.

Medication	Gene	What the guidance says
Aripiprazole, brexpiprazole	CYP2D6	Lower dose for poor metabolizers (DPWG; Health Canada and FDA labels)
Risperidone	CYP2D6	Lower dose for poor metabolizers; for ultrarapid metabolizers, an alternative medication or careful dose adjustment (DPWG)
Haloperidol	CYP2D6	Lower dose for poor metabolizers; higher dose or an alternative for ultrarapid metabolizers (DPWG)
Pimozide	CYP2D6	Lower maximum dose for poor and intermediate metabolizers (DPWG; FDA label)
Quetiapine	CYP3A4	For poor metabolizers, an alternative for depression or a lower dose for other uses (DPWG)
Atomoxetine (ADHD)	CYP2D6	Dose adjustment based on metabolizer status (CPIC)
Olanzapine, clozapine	CYP1A2, CYP2D6	No dose change based on genes alone (DPWG); smoking has a larger effect (see below)

The DPWG notes that testing for these antipsychotics is most useful for individual patients, for example those who have had side effects or a poor response, rather than for everyone starting treatment.

Which pharmacogenetic tests are best for psychiatric medications?

Several types of genetic tests are available. Some tests focus only on psychiatric medications and use their own proprietary rules to interpret the results. They often include psychiatry-specific genes such as SLC6A4 (the serotonin transporter), HTR2A (a serotonin receptor), DRD2 (a dopamine receptor), COMT or MTHFR, where the evidence is inconsistent. A comparison of commercial tests found that they often disagreed on medication recommendations for the same patient. Lab results for cholesterol or blood sugar should be the same whichever lab you use. Shouldn't pharmacogenetic results be standardized too?

CPIC and DPWG write that standard. Their guidelines translate genetic results into metabolizer status (poor, intermediate, normal, rapid or ultrarapid) and give clear prescribing recommendations. When CPIC reviewed SLC6A4 and HTR2A for antidepressants in 2023, it found the evidence insufficient to guide prescribing. Tests that rely on such psychiatry-specific markers can therefore give advice that guidelines don't support.

Pillcheck follows CPIC guidelines and reports according to Health Canada and FDA drug labels.

What does a pharmacist medication review add?

Your DNA is only part of the picture. Age, biological sex, other medications, diet and smoking can all change how well a medication works and how well you tolerate it. The Pillcheck service includes a medication review by a clinical pharmacist trained in pharmacogenetics, who looks at your medication history together with your DNA results and lifestyle.

For example, smoking speeds up the breakdown of clozapine and olanzapine, so smokers may need higher doses. When someone stops smoking, levels of these medications can rise quickly and the dose may need to be lowered. The pharmacist will flag this for your doctor.

For women on birth control pills or hormone replacement therapy, the dose of some medications may need significant adjustment. Estrogen speeds up the clearance of the mood stabilizer lamotrigine, so its levels can fall by about half after starting an estrogen-containing contraceptive, and a higher dose may be needed. When hormonal contraception is stopped, the dose may need to be lowered.

Flagging interactions with other medications you take helps your doctors adjust treatment safely across all your conditions.

Does DNA-guided treatment improve outcomes?

Most of the evidence comes from depression. A meta-analysis of 13 trials with 4,767 patients found that people whose antidepressant treatment was guided by pharmacogenetic testing were 41% more likely to reach remission. A Canadian trial using Pillcheck found greater improvement in depression, anxiety and disability than with usual care. Evidence for antipsychotics is mainly from studies of drug levels and side effects, which is what the DPWG recommendations are based on.

Is pharmacogenetic testing covered by insurance?

Many insurance providers in the US and Canada now include this type of testing in their benefits plans or reimburse the cost through Healthcare Spending Accounts (HCSA). Consider Pillcheck as a preferred option and discuss it with your healthcare provider.

Pillcheck testing is performed in CAP- and COLA-accredited clinical genetic laboratories located in Canada. Pillcheck reports on 24 genes, increasing coverage with new guidelines and drug labels (see the genes tab), and covers 355 medications, which account for over 70% of dispensed prescriptions. The Pillcheck test panel ensures high accuracy for people of non-European and admixed ancestries. Your results last a lifetime, report updates are free of charge, and it's easy to share your results with your doctor.

Summary

Antipsychotics and mood stabilizers can help with many mental health conditions, and some work better than others for specific symptoms.
Genes such as CYP2D6 and CYP3A4 affect the dose of several antipsychotics, including aripiprazole, risperidone, haloperidol and quetiapine.
Choose a pharmacogenetic test that follows CPIC and DPWG guidelines rather than proprietary psychiatry-specific rules, so recommendations are consistent across all your medications.
A pharmacist medication review adds context such as smoking, hormones and drug interactions.

Frequently asked questions

Can a DNA test tell me which antipsychotic will work?

No test can guarantee that. Pharmacogenetic testing shows how your body is likely to process a medication, which helps your doctor choose a suitable dose or avoid a medication that is likely to cause side effects.

Does smoking affect psychiatric medications?

Yes. Smoking speeds up the breakdown of clozapine and olanzapine. Tell your doctor or pharmacist if you start or stop smoking, as the dose may need to change.

Does Pillcheck report HLA genes?

No. HLA genes are linked to rare but serious allergic reactions to some medications, including the mood stabilizers carbamazepine, oxcarbazepine and phenytoin. We don't include HLA results because they can easily be misread: carrying a risk variant doesn't mean you will react, and not carrying a known variant doesn't mean you're safe, because many risk variants are not yet known or tested. Whatever your results, watch for a rash, fever, blistering or mouth sores after starting a new medication, and contact a healthcare provider right away if they appear. If your doctor recommends HLA testing, they can order it through a clinical lab.