SSRIs (Selective Serotonin Reuptake Inhibitors): How They Work, Uses, and Side Effects
Updated: 6 days ago
Written and medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: October 2026 · How we review
Quick Answer: What are SSRIs?
SSRIs (selective serotonin reuptake inhibitors) are the most commonly prescribed type of antidepressant, and they work by keeping serotonin active in the brain for longer. They treat depression, anxiety disorders, OCD, PTSD and bulimia. Most people feel better 4 to 6 weeks after reaching their treatment dose. Never stop an SSRI suddenly; your doctor will lower the dose slowly. [1]
What the research says
All antidepressants beat placebo for depression. A review of 522 trials with 116,477 adults found every one of 21 antidepressants worked better than placebo. Escitalopram, sertraline, citalopram and fluoxetine were among the best tolerated, with fewer people stopping treatment. (Cipriani et al., Lancet, 2018)
Higher doses help a little but cause more side effects. In 40 studies with 10,039 people, higher SSRI doses were slightly more effective, with the benefit leveling off around the equivalent of 50 mg of fluoxetine. Higher doses also led more people to quit because of side effects. (Jakubovski et al., Am J Psychiatry, 2016)
Stopping symptoms are real but usually not severe. Across 79 studies and 21,002 patients, 31% had at least one discontinuation symptom after stopping an antidepressant, versus 17% after stopping placebo. Severe symptoms affected about 2.8%. (Henssler et al., Lancet Psychiatry, 2024)
Key takeaways
SSRIs are usually the first antidepressant doctors choose because side effects tend to be fewer and milder.
They take time: usually 4 to 6 weeks, sometimes 9 to 12 weeks.
They work well alongside talk therapy such as cognitive behavioral therapy (CBT).
Some medicines and supplements interact with SSRIs, so tell your doctor everything you take.
Stopping suddenly can cause discontinuation symptoms, especially after 6 weeks or more of use.
What are SSRIs?
SSRIs are a common class of antidepressant medicines that change the activity of serotonin, a chemical that affects your mood and many other body and brain functions. [1]
There are several types of antidepressants. SSRIs are usually the first choice because they tend to cause fewer and milder side effects than older options. [1]
Taking an SSRI is not a sign of personal weakness. These medicines are widely used and can make a real difference, both mentally and physically.
How do SSRIs work?
SSRIs work by blocking the reabsorption (reuptake) of serotonin, so this chemical messenger stays active in the brain for longer. Serotonin is a neurotransmitter, a chemical messenger that helps different parts of your brain talk to each other. [1]
Here is what happens, step by step:
Serotonin is released. One nerve cell sends serotonin across a tiny gap to the next cell.
It is normally reabsorbed. After delivering its message, the sending cell pulls serotonin back in. This is called reuptake.
SSRIs block reuptake. Serotonin stays active in the brain for a longer time.
Serotonin helps regulate many functions:
Body or brain function | Why it matters |
Mood | Central to depression and anxiety |
Sleep | Sleep changes are common in mood conditions |
Appetite | Linked to eating patterns and weight |
Memory | Plays a role in thinking and recall |
Libido | Explains why sexual side effects can happen |
Social behavior | Affects how you feel and act around others |
Source: [1]
Which medications are SSRIs?
The SSRI medications are citalopram, escitalopram, fluoxetine, fluvoxamine, paroxetine, sertraline, vilazodone and vortioxetine. [1]
Generic name | Brand name(s) |
Citalopram | Celexa® |
Escitalopram | Lexapro® |
Fluoxetine | Prozac®, Sarafem™ |
Fluvoxamine | Luvox® |
Paroxetine | Paxil™, Pexeva®, Brisdelle™ |
Sertraline | Zoloft® |
Vilazodone | Viibryd® |
Vortioxetine | Trintellix® |
Source: [1]
Brand names above are those used in the United States. Names can differ in other countries, so check with your pharmacist.
What do SSRIs treat?
SSRIs treat depression, several anxiety disorders, OCD, PTSD, bulimia, premenstrual dysphoric disorder and menopause symptoms, and doctors sometimes prescribe them for other conditions too. [1]
Approved uses
SSRIs are approved by the U.S. Food and Drug Administration (FDA) to treat:
Condition | Learn more |
Major depressive disorder (MDD) | |
Generalized anxiety disorder (GAD) | |
Panic disorder | |
Social anxiety disorder (social phobia) | |
Obsessive-compulsive disorder (OCD) | — |
Post-traumatic stress disorder (PTSD) | |
Bulimia nervosa | |
Premenstrual dysphoric disorder (PMDD) | — |
Menopause symptoms |
Source: [1]
Off-label uses
Doctors sometimes prescribe SSRIs for other conditions. This is called off-label use. Examples include: [1]
Binge eating disorder
Body dysmorphic disorder
Chronic pelvic pain syndrome
Fibromyalgia
Premature ejaculation
How long do SSRIs take to work?
SSRIs usually take 4 to 6 weeks to work after you reach a therapeutic (full treatment) dose, so they do not work overnight. [1]
For some people, it takes longer: 9 to 12 weeks. If you don't feel better by then, check in with your doctor. They may adjust your treatment plan. [1]
What are the benefits of SSRIs?
The main benefit of SSRIs is that they help manage symptoms of depression, anxiety and many other conditions, usually with mild or minimal side effects. [1]
Help manage symptoms of depression, anxiety and many other conditions.
Generally well tolerated, with mild or minimal side effects.
Often work well when combined with talk therapy, such as cognitive behavioral therapy (CBT).
Can help you get back to feeling like yourself.
What are the side effects of SSRIs?
The most common side effects of SSRIs are dizziness, dry mouth, headache, stomach upset, sexual problems, sleep changes and weight gain, while serious risks are rare. [1]
Common side effects
Dizziness
Dry mouth
Headache
Stomach and gut upset
Sexual problems
Sleep disturbances
Weight gain
Each SSRI has its own side effect profile. Ask your doctor or pharmacist what to expect from yours. For more on sexual side effects, see our guide to depression and sex.
Rare but serious risks
Risk | What it is | What to do |
Serotonin syndrome | Too much serotonin builds up. Signs: confusion, fast heart rate, fever, stiff muscles. | Call your doctor or go to the nearest emergency room. Read more |
QT prolongation | The heart's electrical system takes too long to reset between beats. | Can be life-threatening if untreated, so it needs medical care. |
Suicidal thoughts | People under 25 may be at higher risk of new or worsening suicidal thoughts. | Contact your doctor right away. |
Discontinuation syndrome | Dizziness, flu-like aches or anxiety after stopping suddenly. | Never change your dose without your doctor. Read more |
Source: [1]
If you are thinking about suicide, reach out now. Contact your doctor or your local emergency number. In the U.S., call or text 988 to reach the 988 Suicide and Crisis Lifeline, available 24/7.
What interacts with SSRIs?
SSRIs can interact with blood thinners, NSAID pain relievers, triptans, St. John's wort, dextromethorphan cough medicines and other antidepressants. [1]
Type | Examples |
Blood clot–preventing medicines | Low-dose aspirin, clopidogrel |
Pain relievers (NSAIDs) | Ibuprofen, diclofenac, naproxen |
Migraine medicines | Triptans |
Herbal supplements | St. John's wort |
Over-the-counter cough medicines | Dextromethorphan |
Other antidepressants | Any other antidepressant |
Source: [1]
This list is not complete. Never take an SSRI with an MAOI antidepressant, such as phenelzine, or within 14 days of stopping one, because this can cause dangerous serotonin syndrome. Tell your doctor about every medicine and supplement you take, including natural antidepressants, so they can confirm an SSRI is the safest choice for you.
Can you drink alcohol while taking an SSRI?
It is best to avoid alcohol while taking an SSRI. Alcohol is a depressant. It may interfere with how well the medicine works and can sometimes make depression worse. If you have concerns about drinking, talk to your doctor. [1]
Are SSRIs safe during pregnancy?
SSRIs have been shown to cause some negative effects in a developing baby, but stopping them during pregnancy also carries risks because depression may get worse without treatment. [1]
If you are pregnant or planning a pregnancy, talk to your doctor. They will explain the risks and benefits and help you decide what's best. See also our guide to prenatal depression.
How do you stop taking an SSRI safely?
You stop taking an SSRI safely by having your doctor lower the dose gradually rather than stopping all at once. [1]
Stopping suddenly can trigger antidepressant discontinuation syndrome. These symptoms usually happen if you've taken the medicine for 6 weeks or longer. [1]
When should you call a doctor about an SSRI?
Call your doctor about an SSRI if you don't feel better after 9 to 12 weeks, if side effects bother you, or before you change your dose, get pregnant or start a new medicine. [1]
You don't feel better after 9 to 12 weeks at your treatment dose.
Side effects bother you or don't fade.
You want to change your dose or stop.
You are pregnant or planning a pregnancy.
You start a new medicine or supplement.
Go to the emergency room if you have confusion, a fast heart rate, fever or stiff muscles, or if you have thoughts of suicide. [1]
Conclusion
SSRIs are the most widely used antidepressants for good reason. They treat a long list of conditions, and their side effects are usually mild.
The keys to success are patience, honesty with your doctor about every medicine you take, and never stopping on your own. Paired with talk therapy, an SSRI can help you feel like yourself again.
Next step: Save or print this page and bring it to your next appointment. Use it to ask your doctor which SSRI fits you, what side effects to watch for, and how long to wait before judging results. Explore more plain-language guides in our Diseases & Conditions library, starting with Antidepressants: Understanding Mental Health Medications and Anxiolytics: Understanding Anti-Anxiety Medications.
FAQ
What does SSRI stand for?
SSRI stands for selective serotonin reuptake inhibitor. It is a type of antidepressant that keeps serotonin active in the brain for longer.
What are the most common SSRIs?
SSRIs as a group are the most commonly prescribed antidepressants. Common examples include sertraline, escitalopram, fluoxetine, citalopram and paroxetine.
How long does it take for an SSRI to start working?
An SSRI usually takes 4 to 6 weeks to work after you reach a full treatment dose. Some people need 9 to 12 weeks.
What are the most common SSRI side effects?
The most common SSRI side effects are dizziness, dry mouth, headache, stomach upset, sexual problems, sleep changes and weight gain.
Can SSRIs treat anxiety?
Yes, SSRIs can treat anxiety. They are approved for generalized anxiety disorder, panic disorder, social anxiety disorder, OCD and PTSD.
Can I stop taking an SSRI on my own?
No, you should not stop taking an SSRI on your own. Stopping suddenly can cause dizziness, flu-like aches and anxiety, so your doctor will lower your dose gradually.
Can I drink alcohol on an SSRI?
It is best to avoid alcohol while taking an SSRI. Alcohol can reduce how well the medicine works and may worsen depression.
Can I take ibuprofen with an SSRI?
Ibuprofen and other NSAIDs can interact with SSRIs. Ask your doctor or pharmacist before combining them.
Are SSRIs safe during pregnancy?
SSRIs carry risks during pregnancy, and so does stopping them, because depression may get worse without treatment. Your doctor will help you weigh the risks and benefits.
What is serotonin syndrome?
Serotonin syndrome is a rare but serious reaction that happens when too much serotonin builds up. Signs include confusion, a fast heart rate, fever and stiff muscles, and it needs emergency care.
Is taking an SSRI a sign of weakness?
No, taking an SSRI is not a sign of weakness. SSRIs are widely used medicines that can make a big difference to how you feel.
Further reading
Related Reading
SNRIs Explained: Uses, Side Effects, and How Long They Take to Work explains how SNRI antidepressants work and how they differ from SSRIs.
Antidepressant Discontinuation Syndrome: Symptoms, Causes, and How to Stop Safely explains withdrawal symptoms and how to stop an antidepressant safely.
Serotonin Syndrome Guide: Symptoms, Causes, Diagnosis, and Treatment describes the warning signs and treatment of serotonin syndrome.
What Is Clinical Depression (Major Depressive Disorder)? Symptoms, Causes, Diagnosis and Treatment covers the symptoms, causes and treatment of major depression.
References
Cleveland Clinic. Selective Serotonin Reuptake Inhibitors: Uses & Side Effects. Cleveland Clinic. Last updated September 26, 2025. https://my.clevelandclinic.org/health/treatments/24795-ssri
Cipriani A, Furukawa TA, Salanti G, et al. Comparative efficacy and acceptability of 21 antidepressant drugs for the acute treatment of adults with major depressive disorder: a systematic review and network meta-analysis. Lancet. 2018;391(10128):1357-1366. PMID 29477251. https://doi.org/10.1016/S0140-6736(17)32802-7
Jakubovski E, Varigonda AL, Freemantle N, et al. Systematic review and meta-analysis: dose-response relationship of selective serotonin reuptake inhibitors in major depressive disorder. Am J Psychiatry. 2016;173(2):174-183. PMID 26552940. https://doi.org/10.1176/appi.ajp.2015.15030331
Henssler J, Schmidt Y, Schmidt U, et al. Incidence of antidepressant discontinuation symptoms: a systematic review and meta-analysis. Lancet Psychiatry. 2024;11(7):526-535. PMID 38851198. https://doi.org/10.1016/S2215-0366(24)00133-0
Medical disclaimer
This article is for general education and does not replace advice from your doctor, psychiatrist, pharmacist or another qualified healthcare professional. Never start, change or stop an SSRI without your doctor's guidance. If you have thoughts of suicide or signs of serotonin syndrome, seek emergency care right away.
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