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Antidepressants not working: four alternative medications your doctor should consider

Ruslan Dorfman, PhD, MBA3 Nov 2026

Depression and anxiety are among the most common reasons people see a family doctor, and antidepressants are often the first medication tried. But many people do not feel better on their first antidepressant, which can lead to several trials of different medications, each taking weeks. By the time someone is referred to a psychiatrist, they may have waited months. Understanding why an antidepressant is not working can help you and your doctor choose the next step sooner. Here are the most common reasons, the four medications guidelines recommend when the real diagnosis is bipolar depression, and how pharmacogenetic testing can help.

Why might my antidepressant not be working?

There are many possible reasons, and often more than one applies:

The dose or the time is not enough. Antidepressants usually take two to six weeks to work, and the first dose may be too low.
Your body breaks the medication down too quickly or too slowly. Most selective serotonin reuptake inhibitors (SSRIs) are broken down by the liver enzymes CYP2C19 and CYP2D6. Ultrarapid metabolizers may clear the drug before it can work, while poor metabolizers can build up high levels and have side effects that make them stop.
Other medications or substances interfere. Drug interactions, alcohol and cannabis can all reduce benefit or increase side effects.
Another health issue is involved. Thyroid problems, sleep disorders, chronic pain, anxiety disorders and substance use can all make depression harder to treat.
The medication is not taken regularly, often because of side effects.
The diagnosis is different. Some people treated for depression actually have bipolar disorder, which needs a different approach.

Pharmacogenetic tests like Pillcheck can help with one important piece of this puzzle: whether your genes make a particular antidepressant or dose a poor fit for you. Experts note that, unlike measuring drug levels in the blood, a genetic test does not require waiting until the medication reaches a steady level, and the results stay the same for life (Fabbri and Serretti, Psychiatric Times).

Could it be bipolar disorder?

Bipolar disorder causes periods of depression and periods of abnormally elevated or irritable mood. In bipolar I disorder, people have had at least one episode of mania: days of very high energy, little need for sleep, racing thoughts and risky behaviour that seriously affect daily life. In bipolar II disorder, people have had at least one major depressive episode and at least one milder episode of elevated mood called hypomania, but never full mania.

Because the depressive episodes are often longer and more frequent than the elevated ones, bipolar disorder is often first diagnosed as depression. A diagnosis of bipolar disorder can only be made once an episode of mania or hypomania has been recognized, so it can take years to be identified. Features that suggest a depression may be part of bipolar disorder include:

Depression that started early, before about age 25.
Depression with psychotic features, such as hallucinations or delusions.
A family history of bipolar disorder.
Irritability, agitation, manic symptoms or rapid mood cycling after starting an antidepressant.
Atypical features, such as sleeping too much, increased appetite and a heavy feeling in the arms or legs.
Many short, recurring episodes of depression.

This matters because antidepressants alone can trigger mania, hypomania or faster mood cycling in people with bipolar disorder. In a large clinical trial, adding an antidepressant to a mood stabilizer did not improve recovery from bipolar depression compared with placebo. If you recognize these features, talk to your doctor about a referral to a psychiatrist for a diagnostic review.

What are the four alternatives for bipolar depression?

The Canadian Network for Mood and Anxiety Treatments (CANMAT) and the International Society for Bipolar Disorders (ISBD) guidelines recommend these first-line options for depression in bipolar I disorder, alone or in combination:

Quetiapine, an antipsychotic that is also first-line for bipolar II depression.
Lurasidone, an antipsychotic, alone or added to lithium or divalproex.
Lithium, a mood stabilizer that also lowers the risk of suicide and of future episodes.
Lamotrigine, a mood stabilizer used alone or added to other treatment, which must be started at a low dose and increased slowly to lower the risk of a serious rash.

The guidelines recommend against antidepressants alone in bipolar I disorder. In bipolar II disorder, some antidepressants are considered second-line options in selected people, with close monitoring. Mania itself is treated differently: lithium, quetiapine, divalproex, asenapine, aripiprazole, paliperidone, risperidone and cariprazine are first-line options for acute mania. A psychiatrist will choose a plan based on the type of bipolar disorder, the current episode, side effects and your preferences.

What if it isn’t bipolar disorder?

Most people whose first antidepressant does not work have major depressive disorder, not bipolar disorder, and there are effective next steps. The CANMAT 2023 guidelines for major depression recommend first checking the diagnosis, dose, duration and other health issues, then options such as:

Increasing the dose or switching to a different antidepressant.
Adding another medication, such as aripiprazole, brexpiprazole or quetiapine.
Adding or switching to an evidence-based psychotherapy, such as cognitive behavioural therapy.
Neuromodulation treatments, such as repetitive transcranial magnetic stimulation (rTMS) or electroconvulsive therapy (ECT), and, for treatment-resistant depression, esketamine.

How can pharmacogenetic testing help?

Pharmacogenetic results can help at every step:

Antidepressants. The Clinical Pharmacogenetics Implementation Consortium (CPIC) gives dosing advice based on CYP2C19 for sertraline, citalopram and escitalopram, and on CYP2D6 for paroxetine, fluvoxamine and other antidepressants.
Antipsychotics. Aripiprazole, brexpiprazole and risperidone have dosing guidance based on CYP2D6 in drug labels or Dutch Pharmacogenetics Working Group guidelines. Quetiapine and lurasidone are broken down mainly by CYP3A4, so interactions with medications that block or speed up this enzyme are important.
Mood stabilizers. Lithium is cleared by the kidneys and has no pharmacogenetic guidance. Lamotrigine and divalproex are mainly affected by other medications rather than by the genes on a pharmacogenetic panel.

If your results show that you are a normal metabolizer and your antidepressant still is not working or causes intolerable side effects, the cause is less likely to be how your body breaks the drug down. That can be a useful prompt for your doctor to look more broadly, including at the diagnosis.

A Pillcheck test reports CYP2D6, CYP2C19, CYP3A4 and other genes that affect antidepressants, antipsychotics and many other medications. A pharmacist reviews your results together with all your medications, and your report can be shared with your doctor and psychiatrist.

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, and report updates are free of charge.

Summary

Antidepressants may not work because of the dose, time, drug metabolism, interactions, other health issues, irregular use or a different diagnosis.
Bipolar disorder is often first diagnosed as depression. Early onset, a family history and mood changes on antidepressants are warning signs.
For bipolar I depression, CANMAT/ISBD first-line options include quetiapine, lurasidone, lithium and lamotrigine. Antidepressants alone are not recommended.
For major depression that does not respond, options include switching, adding a medication, psychotherapy and neuromodulation.
Pharmacogenetic testing helps choose antidepressants and antipsychotics and their doses, and a normal result can prompt a broader review.

Frequently asked questions

How long should I wait before deciding an antidepressant is not working?

Usually about four to six weeks at an adequate dose, although some improvement often appears within two weeks. If you have no improvement at all after two to four weeks, or side effects are hard to tolerate, talk to your doctor. Do not stop suddenly.

Can a genetic test diagnose bipolar disorder?

No. Bipolar disorder is diagnosed by a clinician based on your symptoms and history. Pharmacogenetic testing shows how your body handles medications; it does not diagnose mental health conditions.

Are quetiapine and lurasidone the same as antidepressants?

No. They are antipsychotic medications that also treat bipolar depression. Lithium and lamotrigine are mood stabilizers. Each has different side effects and monitoring needs.

Should I stop my antidepressant if I think I might have bipolar disorder?

Do not stop on your own. Talk to your doctor promptly, especially if you notice irritability, racing thoughts or a reduced need for sleep, and ask about a psychiatric assessment.