How Long Does It Take for Antidepressants to Work?

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Most antidepressants don't provide instant relief of symptoms related to depression, anxiety, and other conditions for which they're prescribed. Rather, you must take them routinely and consistently for several weeks or even months before you notice changes. Here are a few guidelines on how long antidepressants take to work.

What Are Antidepressants?

Clinicians frequently prescribe antidepressants to help reduce symptoms of depression, anxiety, obsessive-compulsive disorder (OCD), social anxiety disorder (SAD), agoraphobia, and panic disorder. These medications work by affecting the brain's neurotransmitters—chemical messengers that are responsible for regulating sleep, mood, anxiety, motivation, and other functions and states. They generally fall into a few classes.

Common Classes of Antidepressants and Examples

  • Selective serotonin reuptake inhibitors (SSRIs): Prozac (fluoxetine); Paxil and Pexeva (paroxetine); Zoloft (sertraline); Celexa (citalopram); Lexapro (escitalopram)
  • Serotonin and norepinephrine reuptake inhibitors (SNRIs): Cymbalta (duloxetine); Effexor XR (venlafaxine); Pristiq (desvenlafaxine); Fetzima (levomilnacipran)
  • Tricyclic antidepressants (TCAs)​: Tofranil (imipramine); Pamelor (nortriptyline); amitriptyline; doxepin; Norpramin (desipramine) 
  • Monoamine oxidase inhibitors (MAOIs): Parnate (tranylcypromine); Nardil (phenelzine); Marplan (isocarboxazid); Emsam (selegiline)
  • Atypical antidepressants: Trazodone; Remeron (mirtazapine); Trintellix (vortioxetine); Viibryd (vilazodone); Wellbutrin SR and Wellbutrin XL (bupropion); and more

Most are available in tablet form. Emsam is absorbed through a skin patch.

Clinicians often define "treatment response" as about a 50% decrease in the Hamilton Depression Rating Scale (HAM-D) score compared to the patient's initial (baseline) score. Although there's no universal, definitive milestone for "onset of improvement," this generally ranges from about a 20% to 33% decrease in HAM-D scores.

How Long Different Types of Antidepressants Take to Work

Antidepressants vary by type in the time they take to work, because each class works differently. In any case, pou probably won't see significant improvement in your symptoms for several weeks after you begin your antidepressant dosing regimen. Here are a few general guidelines on when you'll likely begin to see some relief from your symptoms. Note that biomarkers may not reach optimal levels for several weeks or months after these periods.

  • Selective Serotonin Reuptake Inhibitors (SSRIs): About six weeks
  • Serotonin and Norepinephrine Reuptake Inhibitors (SNRIs): One to four weeks
  • Tricyclic Antidepressants (TCAs): Two to four weeks
  • Monoamine Oxidase Inhibitors (MAOIs): As early as two weeks and up to six

What Is a Biomarker?

A biomarker (short for "biological marker") is a molecule in the body that signals some condition or process. Healthcare providers and researchers use biomarkers in diagnosis, treatment, and testing—for example, to check how well a cancer treatment is working or to detect high cholesterol.

What to Expect When Starting an Antidepressant

Once you start taking your antidepressant, you might feel a bit worse before you feel better. Researchers used to believe that the initial boost in energy an antidepressant sometimes provides explains the increased risk of harmful behaviors. However, newer research on SSRIs (the most commonly prescribed class) indicates that this occurs because antidepressants work on different chemicals in your body, and they each reach their optimum levels at different times.

When your antidepressant does start helping, don't stop taking it because you feel better. This is a common mistake, akin to someone with diabetes ceasing their insulin regimen: You'll require your medication to maintain the better health toward which it is moving you, and stopping it suddenly might mean the return of your symptoms—along with some unpleasant, possibly dangerous, side effects.

Possible Side Effects of Antidepressants

Common side effects of taking antidepressants include:

  • Sleep disturbances
  • Headaches
  • Fatigue
  • Dizziness
  • Lightheadedness
  • Dry mouth
  • Nervousness
  • Increased sweating
  • Sexual side effects
  • Blurred vision
  • Nausea

This list is only some of the side effects you can face while taking an antidepressant. You may experience one or more of these, or none at all. Talk with your healthcare provider about any concerning symptoms.

It's important not to stop taking your antidepressant without your prescriber's supervision because it's causing side effects or seemingly not working; your body may just need time to adjust. To ease the transition, you might be prescribed a very low dose at first that is gradually increased. These side effects typically subside and become much more manageable over time.

Managing Your Condition While Waiting for Results

Your doctor may initially prescribe a benzodiazepine (an anti-anxiety medication) along with your antidepressant. Benzodiazepines allow for a faster sense of symptom alleviation.

Benzodiazepines carry a risk for dependence and abuse, so your doctor may take you off this medication once the antidepressant reaches its full benefit.

Coping With Side Effects

If side effects are persistent and become difficult to manage, consult your doctor about the possibility of changing the dosage or medication to better fit your needs.

Beware of Discontinuation Syndrome

Never stop taking your antidepressant without consulting your healthcare provider. Discontinuing your medication suddenly can cause antidepressant discontinuation syndrome, a cluster of unpleasant, and in some cases, dangerous effects when your brain chemicals change too quickly. If your clinician decides that a medication change is necessary, they will instruct you on how to taper down safely and as comfortably as possible.

Considering a Change in Drug or Dosage

Your healthcare provider must balance any medication's potential benefits against its risks and side effects. If you and your clinician believe that you have had an adequate trial of antidepressant therapy without significant improvement or if you find the side effects intolerable, a medication change might be in order. Don't undertake a medication change without your doctor's supervision.

A Word From Verywell

Many people must try several different antidepressants before finding what works best—but most do find relief with the right antidepressant, especially when it's combined with psychotherapy. Always follow your healthcare provider's instructions regarding your antidepressant dosage regimen to maximize its benefits and minimize side effects.

Frequently Asked Questions

  • Why does it take so long for antidepressants to work?

    Many antidepressants, such as SSRIs, are dual-acting. That is, they work on different chemicals in your body, and they each reach their optimum levels at different times. Additionally, your body needs time to adjust to these changing levels of neurotransmitters, the chemical messengers that help regulate sleep, mood, anxiety, motivation, and other functions and states.

  • How do antidepressants work?

    Antidepressants affect the levels of chemicals in your brain called neurotransmitters. These chemical messengers help regulate sleep, mood, anxiety, motivation, and other functions and states

  • What happens if you miss a day of antidepressants?

    Depending on the half-life of your specific antidepressant, you might begin to feel sick after just a few hours if you miss a dose. Symptoms vary with the antidepressant and your usual dose, and they run the gamut from irritability and anxiety to fatigue, nausea, and unusual dreams. If you've missed your dose by just a few hours, take it as soon as you remember. If it's closer to the time you'd take it tomorrow, take it then instead.

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Additional Reading
  • American Psychiatric Association. Practice Guidelines for the Treatment of Psychiatric Disorders: Compendium 2006. American Psychiatric Association, 2006.