How Long Does It Take For Antidepressants to Work?

By: Patricia Weiser, PharmD

Antidepressants usually take about two to four weeks to start noticeably improving symptoms of depression, although some people notice changes sooner. 

It may take four to eight weeks or longer to experience the full benefits of the medication. The exact timeline depends on the specific antidepressant, your symptoms, and how your body responds.

If you're starting an antidepressant or wondering whether your current medication is working, understanding what to expect during the first several weeks can help. A healthcare provider can also help you track your progress and decide whether changes to your treatment plan may be needed.

How do antidepressants work?

Antidepressants are prescription medications used to treat depression and certain other mental health conditions, including anxiety disorders. They’re mainly thought to work by affecting chemicals in the brain called neurotransmitters. These chemicals help nerve cells communicate and play a role in regulating mood, emotions, and other functions.

Some neurotransmitters commonly affected by antidepressants include serotonin, norepinephrine, and dopamine. Serotonin plays a role in mood, sleep, and anxiety. Norepinephrine is involved in alertness, attention, and the body's response to stress. Dopamine is involved in motivation, reward, and other functions.

Different types of antidepressants affect these chemicals in different ways. Common examples include:

• Selective serotonin reuptake inhibitors (SSRIs): Medications such as fluoxetine (Prozac), sertraline (Zoloft), and escitalopram (Lexapro) increase serotonin signaling in the brain.
• Serotonin-norepinephrine reuptake inhibitors (SNRIs): Medications such as duloxetine (Cymbalta) and venlafaxine (Effexor XR) increase signaling involving both serotonin and norepinephrine.
• Atypical antidepressants: These medications work differently from SSRIs and SNRIs. For example, bupropion (Wellbutrin XL) affects norepinephrine and dopamine, while mirtazapine (Remeron) affects certain serotonin and norepinephrine pathways.

How long does it take for antidepressants to work? 

Depression symptoms may begin to improve during the first one to two weeks. Many people who improve early still need four to eight weeks to experience the medication's full benefit at a given dose. However, the timeline can vary depending on the specific medication and individual response.

Although individual experiences vary, the following is a general example of how treatment may progress over the first several weeks, based on guidance from the American Psychiatric Association:

These are general estimates, not a fixed schedule. The timing depends on the medication, dose, symptoms, and individual response. A healthcare provider can help assess progress and whether adjustments may be needed. 

How long SSRIs may take to work for anxiety

SSRIs are commonly prescribed for anxiety disorders, including generalized anxiety disorder. As with depression, the anxiety-relieving benefits of SSRIs usually take time.

SSRIs generally take about two to six weeks to start reducing symptoms of generalized anxiety disorder, while full benefits may take longer.

The timeline can depend on the medication, dose, type of anxiety disorder, and individual response. Healthcare providers sometimes start with a lower dose, particularly for people who are sensitive to side effects, and gradually adjust it based on response.

Some people also experience temporarily increased anxiety, nervousness, or restlessness when they first start an SSRI. These effects usually go away as the body adjusts to the medication, but severe or persistent symptoms warrant prompt contact with a healthcare professional. 

In some cases, another anti-anxiety medication is prescribed “as needed” during this initial adjustment period to help relieve symptoms until the SSRI starts working.

Why do antidepressants take so long to work?

Many antidepressants begin affecting neurotransmitters in the brain shortly after you take your first dose, but the changes involved in improving depression symptoms take longer.

For example, SSRIs block serotonin reuptake, a process in which nerve cells take serotonin back up after releasing it. This increases serotonin signaling, but that initial effect alone doesn't fully explain how SSRIs relieve depression.

Over several weeks, antidepressants may also change how brain cells respond to chemical signals and affect proteins involved in brain cell health and communication.

These gradual changes are thought to help explain why antidepressants don't provide their full benefits right away.

How to know if your antidepressant is working

Antidepressants don't always lead to an obvious change in how you feel. Instead, you may notice small improvements that become more noticeable over time.

Some possible signs that your antidepressant is working include:

• Feeling less sad, hopeless, or overwhelmed
• Sleeping better or having more energy
• Feeling more motivated to complete everyday tasks
• Finding it easier to concentrate
• Enjoying favorite hobbies or activities again

Some symptoms may improve before others. For example, sleep or energy levels might improve before a significant change in overall mood becomes noticeable.

Keeping a journal or using a mood-tracking app may help you recognize changes that are otherwise easy to miss. This might include recording mood, sleep, energy, daily activities, and any side effects throughout treatment.

Your healthcare provider may also use a questionnaire, such as the Patient Health Questionnaire-9 (PHQ-9), to monitor depression symptoms.

Common side effects of antidepressants

Not everyone experiences side effects, and the specific effects vary by medication. 

Common antidepressant side effects may include:

• Nausea, diarrhea, or constipation
• Headache or dizziness
• Dry mouth
• Trouble sleeping or drowsiness
• Increased sweating
• Nervousness or restlessness
• Changes in appetite or weight
• Sexual problems, such as erectile dysfunction or trouble reaching orgasm

Bupropion has a different side effect profile from SSRIs and SNRIs because it does not affect serotonin. For instance, it does not commonly cause weight gain or sexual side effects. 

Bupropion can also cause tremors and carries a dose-related risk of seizures. It is contraindicated in people with a seizure disorder or a current or prior diagnosis of anorexia nervosa or bulimia nervosa because these conditions increase seizure risk.

Some early side effects improve within a few weeks, but others may continue. Antidepressants can also cause serious reactions, including serotonin syndrome, seizures, severe allergic reactions, and mania or hypomania.

Seek emergency care for severe reactions, such as seizures, trouble breathing, or possible serotonin syndrome, which may cause fever, confusion, muscle stiffness, and a fast heartbeat.

Antidepressants carry an FDA boxed warning about increased suicidal thoughts and behaviors in children, adolescents, and young adults. New or worsening mood symptoms require prompt attention.

If you or someone you know is struggling or in crisis, help is available. Text or call 988 or chat 988lifeline.org. Support is available 24/7.

When to talk to healthcare provider if you are concerned about your antidepressant working

Regular follow-up appointments help healthcare providers assess whether an antidepressant is working and whether side effects are manageable.

An initial check-in often takes place within two weeks of starting treatment, with additional follow-ups during the following weeks.

Contact your healthcare provider if:

• Depression or anxiety symptoms are worsening.
• You haven't noticed improvement after several weeks.
• Side effects are bothersome or aren't improving.
• You're experiencing unusual changes in mood, agitation, or sleep.You have questions about changing or stopping treatment.

If an antidepressant isn't helping enough, a licensed prescriber can assess whether more time, a dose adjustment, or another treatment approach may be appropriate.

*Based on finalized paid psychiatry visits with a copay. Insurance availability, coverage, and costs vary by state, plan, provider network, and provider availability.