Genetics and ASD: How DNA testing can guide autism treatment

Ruslan Dorfman, PhD, MBA16 Oct 2026

Autism spectrum disorder (ASD) is a common neurodevelopmental condition with a strong genetic basis: changes in hundreds of genes have been linked to it. No medication treats the core features of autism, but medications can help with related problems such as irritability, hyperactivity and inattention, anxiety, depression, sleep problems and seizures. Children and adults with autism are often more sensitive to medication side effects, and many take several medications at once. A pharmacogenetic test shows how a person's body processes many of these drugs and can help choose safer options and doses.

How is autism treated?

The American Academy of Pediatrics 2020 clinical report recommends early behavioural and developmental interventions as the foundation of autism care. Medications are added for specific symptoms or co-occurring conditions when other approaches are not enough. In a Canadian primary care study of 787 autistic patients, 58% were prescribed a psychotropic medication and 37% took two or more at the same time. The most common were methylphenidate, risperidone, lorazepam, fluoxetine and sertraline, and about a third of the drugs prescribed have pharmacogenetic prescribing guidelines.

Symptom or condition	Common medications	Genes
Irritability, aggression, self-injury	Risperidone, aripiprazole	CYP2D6
Hyperactivity, inattention	Methylphenidate, amphetamines, atomoxetine, guanfacine, clonidine	CYP2D6 (atomoxetine)
Anxiety, depression, obsessive-compulsive symptoms	Sertraline, escitalopram, citalopram, fluoxetine	CYP2C19, CYP2D6, CYP2B6
Seizures	Phenytoin, carbamazepine, oxcarbazepine, clobazam, brivaracetam, valproate	CYP2C9, CYP2C19, HLA-B, POLG
Sleep problems	Melatonin	None with guidelines

How do genes affect autism medications?

Most of these medications are broken down by liver enzymes called cytochromes P450 (CYPs). Genetic variations make these enzymes slower or faster. Slow metabolism can raise drug levels and side effects, while fast metabolism can lower drug levels so the medication helps less. Some medications also block these enzymes and raise the levels of other drugs, which matters for people who take several medications. The Pillcheck pharmacogenetic test combines DNA analysis with a pharmacist's review of all medications to help find the safest and most effective options.

Antipsychotics for irritability

Risperidone (Risperdal) and aripiprazole (Abilify) are approved in the United States for irritability associated with autism, including aggression, self-injury and severe tantrums. Common side effects include increased appetite and weight gain, changes in blood sugar and cholesterol, sleepiness and movement side effects. Risperidone can also raise the hormone prolactin, which can cause breast enlargement (gynecomastia) in boys. Weight, blood sugar and cholesterol should be monitored.

Both drugs are broken down by CYP2D6. The Dutch Pharmacogenetics Working Group (DPWG) guideline recommends lower doses of aripiprazole and risperidone for CYP2D6 poor metabolizers, and for ultrarapid metabolizers taking risperidone, another drug or careful dose titration. Drugs that strongly block CYP2D6, such as fluoxetine and paroxetine, have a similar effect: the aripiprazole label recommends halving its dose when it is combined with them. Other antipsychotics follow different pathways: quetiapine is broken down by CYP3A4, and clozapine and olanzapine mainly by CYP1A2.

Medications for hyperactivity and inattention

Hyperactivity and inattention are common in autism, and ADHD medications can help. In a controlled trial in children with autism and hyperactivity, about half responded to methylphenidate (Ritalin), although the benefit was smaller and side effects such as irritability, poor appetite and trouble sleeping were more frequent than in children with ADHD alone. Amphetamine-based stimulants are also used. Non-stimulant options include atomoxetine, guanfacine and clonidine, which may suit children who do not tolerate stimulants or have sleep problems.

Atomoxetine is broken down by CYP2D6, and poor metabolizers have much higher levels. The CPIC atomoxetine guideline gives dosing recommendations based on CYP2D6, including slower dose increases and, if needed, blood level checks. According to the atomoxetine prescribing information on ClinPGx, the US drug label advises that children and teens up to 70 kg who are CYP2D6 poor metabolizers, or who take strong CYP2D6 blockers such as fluoxetine or paroxetine, start at a lower dose (0.5 mg/kg/day) and increase only if symptoms have not improved after 4 weeks and the dose is well tolerated. Read more about the safety of ADHD medications for children.

Antidepressants for anxiety and depression

SSRIs such as sertraline, escitalopram, citalopram and fluoxetine can help with anxiety, depression and obsessive-compulsive symptoms in people with autism. They do not help repetitive behaviours: in a large trial in children with autism, citalopram worked no better than placebo for repetitive behaviour and caused more side effects, such as increased energy, impulsiveness and trouble sleeping. Children with autism often do better with low starting doses and slow increases.

The CPIC 2023 antidepressant guideline recommends dose adjustments or other drugs based on CYP2C19 (citalopram, escitalopram, sertraline), CYP2B6 (sertraline) and CYP2D6 (paroxetine, fluvoxamine). Fluoxetine and paroxetine also block CYP2D6, which can raise the levels of risperidone, aripiprazole and atomoxetine. Read more about choosing antidepressants with a DNA test.

Benzodiazepines and sleep medications

Benzodiazepines such as clonazepam (Rivotril) and lorazepam (Ativan) are sometimes used for severe anxiety or agitation, but only for short periods because of the risk of dependence, sleepiness and paradoxical agitation. Clonazepam is broken down by CYP3A4 and interacts with many medications, while lorazepam is cleared without CYP enzymes and has fewer interactions. For sleep problems, behavioural strategies and melatonin are the usual first steps.

Beta-blockers

Propranolol is sometimes used for anxiety or aggression in autism, although the evidence is limited. Beta-blockers can lower the body's own melatonin and disturb sleep, so a melatonin supplement may help. Metoprolol and, in part, propranolol are broken down by CYP2D6. The CPIC 2024 beta-blocker guideline recommends that CYP2D6 poor metabolizers start metoprolol at the lowest dose and increase it slowly, or use a different beta-blocker; it makes no genetic recommendation for propranolol. Drugs that block CYP2D6, such as fluoxetine and paroxetine, can also raise metoprolol levels.

Antiepileptic medications

Epilepsy is much more common in people with autism than in the general population. Several antiepileptics have genetic considerations:

Phenytoin: CYP2C9 poor and intermediate metabolizers need lower doses, and carriers of HLA-B*15:02 should avoid it because of the risk of severe skin reactions (CPIC).
Carbamazepine and oxcarbazepine: HLA-B*15:02 and, for carbamazepine, HLA-A*31:01 increase the risk of severe skin reactions such as Stevens-Johnson syndrome.
Clobazam and brivaracetam: broken down by CYP2C19; the product labels recommend lower doses for CYP2C19 poor metabolizers.
Valproate (valproic acid, divalproex): must not be used in people with mitochondrial disorders caused by POLG gene variants because of the risk of liver failure. It also carries serious risks in pregnancy.
Levetiracetam, gabapentin and pregabalin are cleared mainly by the kidneys and are not affected by liver enzyme genes.

Pillcheck does not yet report HLA genes. If your child will start carbamazepine, oxcarbazepine or phenytoin, ask your doctor about HLA testing first, especially for people of Southeast Asian ancestry. Read more in Drug allergy and drug intolerance: what is the difference?

Summary

No medication treats the core features of autism, but medications can help with irritability, hyperactivity, anxiety, sleep and seizures.
People with autism are often more sensitive to side effects, so low starting doses and slow increases are common.
CYP2D6 affects risperidone, aripiprazole and atomoxetine; CYP2C19 affects several SSRIs, clobazam and brivaracetam; CYP2C9 and HLA-B affect phenytoin.
Drug interactions, for example fluoxetine raising risperidone or aripiprazole levels, matter as much as genes.
Pillcheck covers many medications used in autism, including antipsychotics, ADHD medications, antidepressants, benzodiazepines, beta-blockers and antiepileptics, and a pharmacist helps your doctor choose the right drug and dose.

Frequently asked questions

Is there a medication for autism?

No medication treats the core features of autism. Risperidone and aripiprazole are approved in the United States for irritability associated with autism, and other medications treat co-occurring conditions such as ADHD, anxiety and epilepsy.

Which gene affects risperidone and aripiprazole?

CYP2D6. Poor metabolizers have higher drug levels and may need lower doses, and drugs such as fluoxetine and paroxetine that block CYP2D6 have a similar effect.

Can children with autism take ADHD medications?

Yes. About half of children with autism and hyperactivity respond to methylphenidate, although side effects are more common. Atomoxetine, guanfacine and clonidine are non-stimulant options.