What Are Selective Serotonin Reuptake Inhibitors (SSRIs)?

Selective serotonin reuptake inhibitors, or SSRIs, were the first antidepressants developed. They are now the most commonly prescribed antidepressant medications. They are prescribed to treat depression but are also used to treat a broader range of depressive disorders, anxiety disorders, and post-traumatic stress disorder (PTSD).

Having depression is common. Depression affects around 6.7% of the population (16.1 million people) of the United States each year, and that's just the people with clinical diagnoses. Medications such as SSRIs, along with other depression treatment options like talk therapy, can make depression a very treatable condition.

This article explains how SSRIs work, what conditions they are used for, and the different types you may encounter on your own mental health journey. You will also learn about the most common side effects and important safety precautions.

Mental health professional prescribes antidepressant

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What Are SSRIs? 

True to their name, SSRIs are medications that inhibit or limit the reuptake of serotonin. Serotonin is the chemical messenger associated with mood, energy, sexual functioning, digestion, and sleep. It is naturally present in the gut, brain, and central nervous system.

By inhibiting the reuptake of serotonin, SSRIs work to increase levels of serotonin in your body. Low levels of serotonin are associated with depression.

Recent research also suggests that SSRIs work by changing nerve cell functioning in the brain.

How Are SSRIs Used?

SSRIs are approved by the Food and Drug Administration (FDA) to treat depression, anxiety, and other mood disorders.

Types 

FDA-approved SSRIs to treat depression, anxiety, and other mood disorders include:

Not every SSRI is approved to treat every mood disorder. 

Possible SSRI Side Effects 

The FDA lists the following common side effects from SSRIs:

Seizures, abnormal bleeding or bruising, and withdrawal symptoms when adjusting medication can be more serious side effects of SSRIs.

Safety and Precautions


SSRIs may not be an option for everyone. Only you and your healthcare provider can decide what, if any, is the right antidepressant for you.

Drug Interactions

If you’re already taking other medications, SSRIs may interact with them, increasing the risk of adverse reactions or symptoms of overdose.

Negative drug interactions usually involve combinations of an SSRI with other psychotropics (psychoactive drugs that alter nervous system functions), especially tricyclic antidepressants and monoamine oxidase inhibitor (MAOI), lithium, clozapine, and methadone. Drug interactions are common with SSRIs, especially with other psychotropics.

Herbal and natural products can also cause drug interactions with SSRIs. Examples include Japanese ginkgo biloba, which can cause hemorrhaging, and ginseng, which can cause serotonin syndrome.

Serotonin Syndrome 

Serotonin syndrome is a potentially life-threatening reaction to having excessive amounts of serotonin in the nervous system. This can happen when taking SSRIs and other substances that impact serotonin known as serotonergic drugs.

Pain medications, certain migraine medications, herbal supplements (such as Saint-John's-wort), and antidepressants like SSRIs fall into this category. It causes:

  • Mental status changes: This may include anxiety, restlessness, disorientation (confusion), and agitated delirium.
  • Autonomic instability: Unconscious changes in nervous system function, which may include sweating, increased heart rate, high body temperature, high blood pressure, vomiting, and diarrhea.
  • Neuromuscular hyperactivity: Changes in muscle activity and control, which may include tremors, involuntary muscle jerks, and overactive reflexes.

Pregnancy

SSRIs are generally considered safe during pregnancy. Untreated depression during pregnancy is not safe for the person or the growing fetus with specific neonatal needs.

Previously, there was a public health advisory for SSRIs during pregnancy due to risk of persistent pulmonary hypertension of the newborn (PPHN), which is a low concentration of oxygen in the blood due to circulation issues. That advisory has since been recalled as it was based on a single published study. Newer data show PPHN is rare, and that doctors should not alter their treatment of depression.

Children and Teens 

Antidepressants carry an FDA black box warning about a risk of increased suicidal thinking and behavior in some individuals under the age of 25.

Benefits of SSRIs may outweigh risks, but close monitoring of children and teens taking antidepressants is necessary.

Suicidal Thoughts 

There is risk of suicidal thinking associated with depression, mood disorders, and antidepressant use, but it's not a direct relationship, nor is it explained simply. A 2021 study demonstrated suicidal thoughts were more likely in the month before starting antidepressants than the month after or at the year-after mark. Results don’t support that SSRI treatment increases the risk of suicidal behavior, but it is possible that SSRI treatment reduces the risk.

When to Stop Treatment 

Depression, like any mental health condition, truly is different for everyone. This means there is no “standard” treatment course for antidepressants. That said, healthcare providers usually recommend taking the medication for six to nine months before deciding to go off them.

However, if you've had three or more recurrences of depression, your provider may recommend maintaining treatment for two years after your symptoms stop or stabilize. Only you and your providers can determine when or if stopping treatment is best for your situation.

How to Find the Right Antidepressant 

The right antidepressant may take trial and error to find. This is because it’s not possible to predict for certain how your body chemistry will respond to the medication.

If one SSRI doesn’t seem to be working–or the side effects are unmanageable–talk to your prescribing provider about trying another antidepressant. This can include another SSRI or another class of drugs like selective norepinephrine reuptake inhibitors (SNRIs).

Summary 

SSRIs are the most commonly prescribed antidepressants. They are used to treat depression, anxiety, and other mood disorders. There are also off-label uses. Some safety precautions exist, but this drug class is generally seen by providers as a safe choice for treating depression.

A Word From Verywell 

Depression is a complex mental health condition with many potential causes and factors that can either work in support of recovery or against treatment efforts. While medications can be a lifesaving tool for people with depression, they are not the only option, nor should they be seen as the only tool for managing depression. You may also want to consider talk therapy, which can help you work through any underlying problems (past or present).

Frequently Asked Questions

  • Which SSRIs are best for treating depression?

    Prozac (fluoxetine) is the most well-researched SSRI for treating depression, but which SSRI is best for you will depend upon individual factors. Only you and your healthcare provider can determine what antidepressant may be most beneficial for your situation. 

  • Are SSRIs only used to treat depression?

    No. SSRIs are used to treat a variety of conditions, including depressive disorders, anxiety disorders, and other mood disorders. Healthcare providers may also prescribe SSRIs for off-label uses, depending on the person’s medical history and health condition.

  • Do selective serotonin reuptake inhibitors help with anxiety?

    Yes. SSRIs are used to treat anxiety. Serotonin impacts a range of moods and emotions, not just depression or happiness. Adequate levels of serotonin are associated with calm along with happiness. 

  • What does "inhibit the reuptake of serotonin" mean?

    the term "inhibit the reuptake of serotonin" means to prevent the reabsorption of serotonin in order to increase overall levels in your body.

  • Can you drink alcohol on SSRIs?

    Drinking alcohol when taking antidepressants is advised against. You should not combine them. Doing so could have side effects like impaired thinking and increased drowsiness.

  • What is the difference between SNRIs and SSRIs?

    The difference is that SSRIs target serotonin only, but SNRIs block or inhibit the reabsorption of serotonin and another chemical messenger associated with mood called norepinephrine. It is used to treat other conditions along with depression, including fibromyalgia. 

20 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. López-Muñoz F, Alamo C. Monoaminergic neurotransmission: the history of the discovery of antidepressants from 1950s until today. Curr Pharm Des. 2009;15(14):1563-1586. doi:10.2174/138161209788168001

  2. American Psychiatric Association. Medications for PTSD.

  3. National Institute of Mental Health. Mental health medications.

  4. Anxiety and Depression Association of America. Understanding anxiety and depression: Did you know? 

  5. Jenkins TA, Nguyen JC, Polglaze KE, Bertrand PP. Influence of tryptophan and serotonin on mood and cognition with a possible role of the gut-brain axis. Nutrients. 2016;8(1):56. doi:10.3390/nu8010056

  6. Harvard Health Publishing. Serotonin: The natural mood booster.

  7. Casarotto PC, Girych M, Fred SM, et al Antidepressant drugs act by directly binding to TRKB neurotrophin receptors. Cell. 2021;184(5):1299-1313.e19. doi:10.1016/j.cell.2021.01.034

  8. Food and Drug Administration. SSRI information.

  9. U.S. Food and Drug Administration. Selective serotonin reuptake inhibitors (SSRIs) information.

  10. Food and Drug Administration. Depression medications.

  11. Food and Drug Administration. Depression medications.

  12. Drug interactions with selective serotonin reuptake inhibitors, especially with other psychotropics. Prescrire Int. 2001 Feb;10(51):25-31.

  13. Woroń J, Siwek M. Unwanted effects of psychotropic drug interactions with medicinal products and diet supplements containing plant extracts. Niepożądane efekty interakcji leków psychotropowych z produktami leczniczymi i suplementami diety zawierającymi wyciągi roślinne. Psychiatr Pol. 2018;52(6):983-996. doi:10.12740/PP/OnlineFirst/80998

  14. American Academy of Family Physicians. Prevention, recognition, serotonin syndrome.

  15. Osbourne LM. Antidepressants and pregnancy: Tips from an expert. Johns Hopkins Medicine.

  16. Food and Drug Administration. FDA Drug Safety Communication: Selective serotonin reuptake inhibitor (SSRI) antidepressant use during pregnancy and reports of a rare heart and lung condition in newborn babies.

  17. U.S. Food and Drug Administration. Suicidality in children and adolescents treated with antidepressants.

  18. Lagerberg T, Fazel S, Sjölander A, Hellner C, Lichtenstein P, Chang Z. Selective serotonin reuptake inhibitors and suicidal behaviour: A population-based cohort study. Neuropsychopharmacol. 2021;47:817–823. doi:10.1038/s41386-021-01179-z

  19. Harvard Health Publishing. Going off antidepressants.  

  20. John M. Eisenberg Center for Clinical Decisions and Communications Science. Treatment options when your SSRI antidepressant is not working well. 2013 Jul 24. In: Comparative Effectiveness Review Summary Guides for Consumers [Internet]. Rockville (MD): Agency for Healthcare Research and Quality (US); 2005-.

By Michelle Pugle
Michelle Pugle, BA, MA, is an expert health writer with nearly a decade of contributing accurate and accessible health news and information to authority websites and print magazines. Her work focuses on lifestyle management, chronic illness, and mental health. Michelle is the author of Ana, Mia & Me: A Memoir From an Anorexic Teen Mind.