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How long does it take for antidepressants to work?

Here’s what to know, including early changes, side effects, and when to contact a professional.

March 13, 2026

Clinically reviewed by Dr. Joshua Cohen, M.D., Ph.D.

10 min read

Clinically reviewed by Dr. Joshua Cohen, M.D., Ph.D.

If you’re struggling with depression, anxiety, obsessive-compulsive disorder, or other common mental health conditions, your doctor may prescribe an antidepressant. These medications don’t address the underlying causes of mental health conditions, but they can ease symptoms and help you feel better.

Many people hope for instant relief when they start an antidepressant. But, unfortunately, that’s not how they work. “You shouldn’t expect to take these medications and feel like a light switch has been flipped and everything is fixed in your life,” says Joshua Cohen, MD, PhD, a psychiatrist and Headway's medical director for clinical quality.

Antidepressants take some time to work, and progress may be subtle or gradual. This is important to remember since many people feel discouraged — or even stop taking their prescriptions — if they don’t see dramatic results right away.

In this guide, we’ll walk through realistic expectations for your antidepressant, how long it takes antidepressants to work, the changes you can expect to see first, and how to know if it’s time to talk to your doctor about switching medications.

Note: This article is for informational purposes only and does not constitute medical advice. Consult a psychiatric provider about your specific treatment needs.

How long does it take for antidepressants to work?

There’s no single answer to the question of how long it takes antidepressants to work. Your response time depends on your symptoms, the drug you’re prescribed, and your body. 

That said, many people feel some positive effects within two weeks of starting a new antidepressant, studies show. Other people need more time to respond. It can take four to eight weeks for an antidepressant to work, Cohen says.

Improvements typically build gradually, rather than coming on all at once. That means the first signs of response may be subtle. “My patients will often say 'I don't feel anything. I don't feel any different,’” Cohen says. “But the people in their lives will see differences. They’re getting out of bed more, they’re doing more, they just seem a little bit brighter or less sad.”

Again, your response to treatment may not look exactly like someone else’s, so it’s best to discuss the specifics of your situation with your doctor or psychiatric care provider. But here’s a rough timeline of how long it might take for your antidepressant to work.

First 1–2 weeks

Here’s the bad news: Right after starting a new antidepressant, you’re likely to have more side effects, like headaches and nausea, than mental health benefits. (More on that later.) You may see some modest improvements, perhaps to your energy or motivation, but the medication probably hasn’t taken full effect yet.

Weeks 2–4

As time passes, your side effects should begin to subside while benefits to your mood get stronger.

Weeks 4–6

By now, you’ve likely noticed improvements in your mood and depression symptoms. If you haven’t, you might consider asking your psychiatric provider about changing your dosage or trying a different antidepressant.

Up to 12 weeks

You’re hopefully stable by this point, feeling few (if any) side effects and sustained improvement to your mental health. Keep in mind, though, that antidepressants are typically long-term prescriptions; you don’t stop taking them as soon as you feel better. Your doctor or psychiatric care provider can help determine how long to take yours.

Types of antidepressants and whether they affect response time

Antidepressants aren’t all the same. There are several medication classes that fall under the umbrella of antidepressants. They all work differently, which can influence the pace and type of changes you see. Some of the major types of antidepressants include:

Selective serotonin reuptake inhibitors (SSRIs)

SSRIs are the most commonly prescribed antidepressants in the U.S., known by brand names such as Prozac (fluoxetine) and Zoloft (sertraline). They work by raising levels of serotonin, a mood-boosting neurotransmitter, in your brain. Generally, you can expect these to work within four to eight weeks, Cohen says.

Serotonin and norepinephrine reuptake inhibitors (SNRIs)

In addition to amping up serotonin, SNRIs such as Cymbalta also raise levels of norepinephrine, a neurotransmitter that’s involved in mood, attention, alertness, and stress. They generally work on about the same timeline as SSRIs.

Tricyclic antidepressants

Tricyclic antidepressants also raise concentrations of serotonin and norepinephrine, and they can help with certain kinds of pain relief. They’re older and come with more side effects than SSRIs and SNRIs, so they’re not commonly prescribed for depression today. They generally take effect in about two to four weeks.

Monoamine oxidase inhibitors (MAOIs)

MAOIs boost levels of beneficial neurotransmitters by neutralizing an enzyme that breaks them down. Like tricyclic antidepressants, they’ve been largely replaced by newer antidepressants such as SSRIs and SNRIs. They often start to work in roughly two to three weeks.

Atypical antidepressants

This is a catch-all term for antidepressants that don’t fit into other classes. Examples include bupropion (sold under brand names including Wellbutrin) and mirtazapine (sold under brand names including Remeron). They all work a bit differently, so you may see effects on different timelines. Bupropion, for example, tends to be “activating” and boosts energy, Cohen says. “The energy effect could happen in the first couple days.”

Why antidepressants don’t work immediately

Why don’t antidepressants kick in immediately? The truth is, these drugs are complex and scientists are still learning about exactly what they do to the brain. But here are some potential reasons their effects may be delayed.

Neurotransmitter regulation 

It’s often said that drugs like SSRIs work by raising levels of key neurotransmitters in the brain — but that’s a bit of an over-simplification, Cohen explains. “The effect probably isn’t due to just changing [neurotransmitter] concentrations,” he says. “What happens is, when you change that concentration, the cells respond,” setting off a domino effect of changes in the brain. It can take weeks for the results of that domino effect to become clear, he says.

Brain circuitry changes related to mood regulation

Another theory is that antidepressants change the way your brain responds to stressors, effectively helping it re-learn how to respond to negative experiences or stimuli. This may include changes to the brain’s circuitry, and that rewiring doesn’t happen overnight.

Medication dosing

When you start a new antidepressant, your psychiatric provider may start you at a low dose and gradually scale up over time. “Some people respond to low doses,” Cohen says, but others don’t see significant changes until they’re taking more.

Trickle-down effects

In some cases, it can be hard to disentangle whether antidepressants are having a direct effect on the brain, or changing aspects of your life that lead to improvements in symptoms, Cohen says. For example, an antidepressant might get your sleep back on track, which could lead to improvements in mood and functioning over time.

What are the side effects of antidepressants?

Unfortunately, many people experience unpleasant side effects before their antidepressant starts to work on their mood and mental health. That leads some people to quit, assuming the medication isn’t working — but try to be patient, Cohen says. “Usually you have the worst side effects in the first couple weeks, but those fade and you feel better” as the drug takes full effect, he says.

Side effects differ from person to person and drug to drug, so it’s best to discuss your specific situation with your doctor. But these are common side effects that you may experience as your antidepressant starts to work:

  • Nausea
  • Headaches
  • Changes in sleep or energy
  • Changes in sexual desire and/or function
  • Weight gain 
  • Dizziness
  • Dry mouth

Signs your antidepressant is starting to work

Remember, the first signs that your antidepressant is working may be subtle. Often, Cohen says, people notice changes in their daily functioning before they feel profound differences in their mood. Things that felt like a chore before — getting out of bed, cleaning, working — may begin to feel easier. 

Other signs that your antidepressant is starting to work could include:

  • Improvements in mood
  • Feeling that negative mental health symptoms are less intense or disruptive
  • Increased energy
  • Better sleep
  • Better focus
  • Feeling more pleasure from activities or experiences

When to contact a mental health professional

If you’ve just started a new antidepressant and aren’t feeling relief, it can be hard to know what to do. Is your antidepressant not working yet, or does it not work for you at all? When should you contact your therapist and ask about trying something else? 

In Cohen’s view, you should contact your doctor or psychiatric care provider if you (or your loved ones) haven’t noticed any improvement whatsoever after two weeks. They can help determine whether the dose or medication needs to be changed, or if you just need to wait a little longer to see its effects.

Some providers might give different advice, he notes. “Alternatively, many other clinicians might recommend waiting four to six weeks,” Cohen says.

Your medication journey is up to you and the medical provider who prescribes your medication. You'll just want to weigh the pros and cons for yourself. Are you unsure if your medication is working, but the side effects aren't bad? It might be worth six weeks to keep trying the meds. But are you experiencing side effects that are too uncomfortable to bear? Maybe waiting six weeks is too long, and a change is needed sooner.

One important caveat: Certain side effects warrant an immediate call to your doctor or mental health provider. If you experience any of the following, do not wait for them to get better. Contact a provider right away if you experience:

  • New or increased suicidal thoughts
  • Blurry vision
  • Severe physical side effects (such as debilitating headaches, constant vomiting, high blood pressure, seizures, or chest pain)
  • Unusual behavioral changes (such as impulsivity or recklessness)
  • Worsening depression, or other new mental health issues

Staying in touch with a medical professional during antidepressant treatment

Patience is part of the process when it comes to starting a new antidepressant. These medications may take time to fully kick in — but when you find the right one, it’s worth the wait. 

How do you know when you’ve found the right one? At the end of the day, you’re the best judge of how well your antidepressant is working and whether its benefits outweigh any side effects you’re experiencing. As a patient, you should always have “an active role in mental health treatment,” Cohen says. Don’t be afraid to advocate for yourself.

Whether you’ve just started a new antidepressant or have been on one for a while, these drugs should always be taken under the care of a qualified mental health professional. Stay in regular contact with your psychiatric care provider, especially if you have questions about your medication, have new or persistent side effects, or are considering a medication change. Don’t quit cold turkey, even if you think your antidepressant isn’t working.

Find care with Headway

Access to timely, in-network mental health care makes it far easier to get your questions answered and find the right antidepressant prescription. As the nation’s largest network of mental health providers who accept insurance, Headway is here to help with that. 

Use Headway’s directory to find therapists and psychiatric care providers in your area. With access to clear information about pricing, insurance, and appointment availability, finding help is quick, easy, and predictable.

This content is for general informational and educational purposes only and does not constitute clinical, legal, financial, or professional advice. All decisions should be made at the discretion of the individual or organization, in consultation with qualified clinical, legal, or other appropriate professionals.

© 2026 Therapymatch, Inc. dba Headway. All rights reserved. No part of this publication may be reproduced without permission.

Medication & prescriptions