Selective serotonin reuptake inhibitors (SSRIs)

This commonly prescribed type of antidepressant can help you overcome depression. Discover how SSRIs improve mood and what side effects they may cause.

By Mayo Clinic Staff

Selective serotonin reuptake inhibitors (SSRIs) are the most commonly prescribed antidepressants. They can ease symptoms of moderate to severe depression, are relatively safe and typically cause fewer side effects than other types of antidepressants do.

How SSRIs work

SSRIs treat depression by increasing levels of serotonin in the brain. Serotonin is one of the chemical messengers (neurotransmitters) that carry signals between brain nerve cells (neurons).

SSRIs block the reabsorption (reuptake) of serotonin into neurons. This makes more serotonin available to improve transmission of messages between neurons. SSRIs are called selective because they mainly affect serotonin, not other neurotransmitters.

SSRIs may also be used to treat conditions other than depression, such as anxiety disorders.

SSRIs approved to treat depression

The Food and Drug Administration (FDA) has approved these SSRIs to treat depression:

  • Citalopram (Celexa)
  • Escitalopram (Lexapro)
  • Fluoxetine (Prozac)
  • Paroxetine (Paxil, Pexeva)
  • Sertraline (Zoloft)

Possible side effects and cautions

All SSRIs are thought to work in a similar way and generally can cause similar side effects, though some people may not experience any. Many side effects may go away after the first few weeks of treatment, while others may lead you and your doctor to try a different drug.

If you can't tolerate one SSRI, you may be able to tolerate a different one, as SSRIs differ in their potencies at blocking serotonin reuptake and in how quickly the body eliminates (metabolizes) the drug.

Possible side effects of SSRIs may include, among others:

  • Nausea, vomiting or diarrhea
  • Headache
  • Drowsiness
  • Dry mouth
  • Insomnia
  • Nervousness, agitation or restlessness
  • Dizziness
  • Sexual problems, such as reduced sexual desire, difficulty reaching orgasm or inability to maintain an erection (erectile dysfunction)
  • Impact on appetite, leading to weight loss or weight gain

Taking your medication with food may reduce the risk of nausea. Also, as long as your medication doesn't keep you from sleeping, you can reduce the impact of nausea by taking it at bedtime.

Which antidepressant is best for you depends on a number of issues, such as your symptoms and any other health conditions you may have. Ask your doctor and pharmacist about the most common possible side effects for your specific SSRI and read the patient medication guide that comes with the prescription.

Safety issues

SSRIs are generally safe for most people. However, in some circumstances they can cause problems. For example, high doses of citalopram may cause dangerous abnormal heart rhythms, so doses over 40 milligrams (mg) a day should be avoided according to the FDA and the manufacturer. They also recommend a maximum daily dose of 20 mg of citalopram for people over age 60.

Issues to discuss with your doctor before you take an SSRI include:

  • Drug interactions. When taking an antidepressant, tell your doctor about any other prescription or over-the-counter medications, herbs or other supplements you're taking. Some antidepressants can interfere with the effectiveness of other medications, and some can cause dangerous reactions when combined with certain medications or herbal supplements.

    For example, SSRIs may increase your risk of bleeding, especially when you're taking other medications that increase the risk of bleeding, such as nonsteroidal anti-inflammatory drugs (NSAIDs), aspirin, warfarin (Coumadin, Jantoven) and other blood thinners.

  • Serotonin syndrome. Rarely, an antidepressant can cause high levels of serotonin to accumulate in your body. Serotonin syndrome most often occurs when two medications that raise the level of serotonin are combined. These include, for example, other antidepressants, certain pain or headache medications, and the herbal supplement St. John's wort.

    Signs and symptoms of serotonin syndrome include anxiety, agitation, high fever, sweating, confusion, tremors, restlessness, lack of coordination, major changes in blood pressure and a rapid heart rate. Seek immediate medical attention if you have any of these signs or symptoms.

  • Antidepressants and pregnancy. Talk to your doctor about the risks and benefits of using specific antidepressants. Some antidepressants may harm your baby if you take them during pregnancy or while you're breast-feeding. If you're taking an antidepressant and you're considering getting pregnant, talk to your doctor about the possible risks. Don't stop taking your medication without contacting your doctor first, as stopping might pose risks for you.

Suicide risk and antidepressants

Most antidepressants are generally safe, but the FDA requires that all antidepressants carry black box warnings, the strictest warnings for prescriptions. In some cases, children, teenagers and young adults under 25 may have an increase in suicidal thoughts or behavior when taking antidepressants, especially in the first few weeks after starting or when the dose is changed.

Anyone taking an antidepressant should be watched closely for worsening depression or unusual behavior. If you or someone you know has suicidal thoughts when taking an antidepressant, immediately contact your doctor or get emergency help.

Keep in mind that antidepressants are more likely to reduce suicide risk in the long run by improving mood.

Stopping treatment with SSRIs

SSRIs aren't addictive. However, stopping antidepressant treatment abruptly or missing several doses can cause withdrawal-like symptoms. This is sometimes called discontinuation syndrome. Work with your doctor to gradually and safely decrease your dose.

Withdrawal-like symptoms can include:

  • General feeling of uneasiness
  • Nausea
  • Dizziness
  • Lethargy
  • Flu-like symptoms

Finding the right antidepressant

People may react differently to the same antidepressant. For example, a particular drug may work better — or not as well — for you than for another person. Or you may have more, or fewer, side effects from taking a specific antidepressant than someone else does.

Inherited traits play a role in how antidepressants affect you. If you have a close relative who responded to a particular antidepressant, tell your doctor, because this could be a good drug choice to start.

In some cases, results of special blood tests, where available, may offer clues about how your body may respond to a particular antidepressant. However, other variables can affect your response to medication.

When choosing an antidepressant, your doctor takes into account your symptoms, any health problems, other medications you take and what has worked for you in the past.

Typically, it may take several weeks or longer before an antidepressant is fully effective and for initial side effects to ease up. Your doctor may recommend some dose adjustments or different antidepressants, but with patience, you and your doctor can find a medication that works well for you.

From Mayo Clinic to your inbox

Sign up for free and stay up to date on research advancements, health tips, current health topics, and expertise on managing health. Click here for an email preview.

To provide you with the most relevant and helpful information, and understand which information is beneficial, we may combine your email and website usage information with other information we have about you. If you are a Mayo Clinic patient, this could include protected health information. If we combine this information with your protected health information, we will treat all of that information as protected health information and will only use or disclose that information as set forth in our notice of privacy practices. You may opt-out of email communications at any time by clicking on the unsubscribe link in the e-mail.

Sept. 17, 2019 See more In-depth

See also

  1. Addison's disease
  2. Adjustment disorders
  3. Adrenal fatigue: What causes it?
  4. Alzheimer's: New treatments
  5. Alzheimer's 101
  6. Understanding the difference between dementia types
  7. Alzheimer's disease
  8. Alzheimer's drugs
  9. Alzheimer's genes
  10. Alzheimer's prevention: Does it exist?
  11. Alzheimer's stages
  12. Ambien: Is dependence a concern?
  13. Antidepressant withdrawal: Is there such a thing?
  14. Antidepressants and alcohol: What's the concern?
  15. Antidepressants and weight gain: What causes it?
  16. Antidepressants: Can they stop working?
  17. Antidepressants: Side effects
  18. Antidepressants: Selecting one that's right for you
  19. Antidepressants: Which cause the fewest sexual side effects?
  20. Antidepressants and pregnancy
  21. Atypical antidepressants
  22. Back pain
  23. Binge-eating disorder
  24. Blood Basics
  25. Borderline personality disorder
  26. Breastfeeding and medications
  27. Dr. Wallace Video
  28. Dr. Mark Truty (surgery, MN) better outcomes with chemo
  29. Can zinc supplements help treat hidradenitis suppurativa?
  30. Hidradenitis suppurativa wound care
  31. Celiac disease
  32. Child abuse
  33. Chronic traumatic encephalopathy
  34. CJD - Creutzfeldt-Jakob Disease
  35. Clinical depression: What does that mean?
  36. Clinical trials for hidradenitis suppurativa
  37. Coconut oil: Can it cure hypothyroidism?
  38. Complete blood count (CBC)
  39. Complicated grief
  40. Compulsive sexual behavior
  41. Concussion
  42. Concussion in children
  43. Concussion Recovery
  44. Concussion Telemedicine
  45. Coping with the emotional ups and downs of psoriatic arthritis
  46. Coping with the stress of hidradenitis suppurativa
  47. COVID-19 and your mental health
  48. Creating a hidradenitis suppurativa care team
  49. Creutzfeldt-Jakob disease
  50. Cushing syndrome
  51. Cyclothymia (cyclothymic disorder)
  52. Delirium
  53. Depression and anxiety: Can I have both?
  54. Depression, anxiety and exercise
  55. What is depression? A Mayo Clinic expert explains.
  56. Depression during pregnancy
  57. Depression in women: Understanding the gender gap
  58. Depression (major depressive disorder)
  59. Depression: Supporting a family member or friend
  60. Diabetes and depression: Coping with the two conditions
  61. Diagnosing Alzheimer's
  62. Did the definition of Alzheimer's disease change?
  63. Dissociative disorders
  64. Vitamin C and mood
  65. Drug addiction (substance use disorder)
  66. Electroconvulsive therapy (ECT)
  67. Fatigue
  68. Fibromyalgia
  69. HABIT program orientation
  70. Hangovers
  71. Hashimoto's disease
  72. Headache
  73. Hidradenitis suppurativa
  74. Hidradenitis suppurativa and biologics: Get the facts
  75. Hidradenitis suppurativa and diet: What's recommended?
  76. Hidradenitis suppurativa and sleep: How to get more zzz's
  77. Hidradenitis suppurativa: Tips for weight-loss success
  78. Hidradenitis suppurativa: What is it?
  79. Hidradenitis suppurativa: When does it appear?
  80. Hidradenitis suppurativa: Where can I find support?
  81. How opioid use disorder occurs
  82. How to tell if a loved one is abusing opioids
  83. Hyperparathyroidism
  84. Hypoparathyroidism
  85. Hypothyroidism: Can calcium supplements interfere with treatment?
  86. Hypothyroidism diet
  87. Hypothyroidism and joint pain?
  88. Hypothyroidism: Should I take iodine supplements?
  89. Hypothyroidism symptoms: Can hypothyroidism cause eye problems?
  90. Hypothyroidism (underactive thyroid)
  91. Insomnia
  92. Insomnia: How do I stay asleep?
  93. Insomnia treatment: Cognitive behavioral therapy instead of sleeping pills
  94. Intervention: Help a loved one overcome addiction
  95. Is depression a factor in rheumatoid arthritis?
  96. Kratom for opioid withdrawal
  97. Lack of sleep: Can it make you sick?
  98. Lecanemab for Alzheimer's disease
  99. Living better with hidradenitis suppurativa
  100. Low blood pressure (hypotension)
  101. Male depression: Understanding the issues
  102. Managing Headaches
  103. Managing hidradenitis suppurativa: Early treatment is crucial
  104. Hidradenitis suppurativa-related health risks
  105. MAOIs and diet: Is it necessary to restrict tyramine?
  106. Marijuana and depression
  107. Mayo Clinic Minute: 3 tips to reduce your risk of Alzheimer's disease
  108. Mayo Clinic Minute: Alzheimer's disease risk and lifestyle
  109. Mayo Clinic Minute New definition of Alzheimer's changes
  110. Mayo Clinic Minute: Prevent migraines with magnetic stimulation
  111. Mayo Clinic Minute: Restless legs syndrome in kids
  112. Mayo Clinic Minute Weathering migraines
  113. Mayo Clinic Minute: Women and Alzheimer's Disease
  114. Medication overuse headaches
  115. Meditation
  116. Memory loss: When to seek help
  117. Mental health: Overcoming the stigma of mental illness
  118. Mental health providers: Tips on finding one
  119. Mental health
  120. Mental illness
  121. Migraine
  122. What is a migraine? A Mayo Clinic expert explains
  123. Migraine medicines and antidepressants
  124. Migraine FAQs
  125. Migraine treatment: Can antidepressants help?
  126. Migraines and gastrointestinal problems: Is there a link?
  127. Migraines and Vertigo
  128. Migraines: Are they triggered by weather changes?
  129. Alleviating migraine pain
  130. Mild cognitive impairment (MCI)
  131. Mindfulness exercises
  132. Monoamine oxidase inhibitors (MAOIs)
  133. Natural remedies for depression: Are they effective?
  134. Nervous breakdown: What does it mean?
  135. New Alzheimers Research
  136. Nicotine dependence
  137. Occipital nerve stimulation: Effective migraine treatment?
  138. Ocular migraine: When to seek help
  139. Opioid stewardship: What is it?
  140. Oppositional defiant disorder (ODD)
  141. Pain and depression: Is there a link?
  142. Pancreatic cancer
  143. Pancreatic Cancer
  144. What is pancreatic cancer? A Mayo Clinic expert explains
  145. Infographic: Pancreatic Cancer: Minimally Invasive Surgery
  146. Pancreatic Cancer Survivor
  147. Infographic: Pancreatic Cancers-Whipple
  148. Perimenopause
  149. Pituitary tumors
  150. Polymyalgia rheumatica
  151. Post COVID syndrome
  152. Premenstrual dysphoric disorder
  153. Premenstrual syndrome (PMS)
  154. Prescription drug abuse
  155. Prescription sleeping pills: What's right for you?
  156. Progressive supranuclear palsy
  157. Psychotherapy
  158. Reducing the discomfort of hidradenitis suppurativa: Self-care tips
  159. Restless legs syndrome
  160. Salt craving: A symptom of Addison's disease?
  161. Schizoaffective disorder
  162. Seasonal affective disorder (SAD)
  163. Seasonal affective disorder treatment: Choosing a light box
  164. Serotonin and norepinephrine reuptake inhibitors (SNRIs)
  165. Sleep disorders
  166. Sleep tips
  167. Soy: Does it worsen hypothyroidism?
  168. Staying active with hidradenitis suppurativa
  169. Stress symptoms
  170. Sundowning: Late-day confusion
  171. Support groups
  172. Surgery for hidradenitis suppurativa
  173. Symptom Checker
  174. Tapering off opioids: When and how
  175. Tinnitus and antidepressants
  176. Transcranial magnetic stimulation
  177. Traumatic brain injury
  178. Treating hidradenitis suppurativa: Explore your options
  179. Treating hidradenitis suppurativa with antibiotics and hormones
  180. Treatment of parathyroid disease at Mayo Clinic
  181. Treatment-resistant depression
  182. Tricyclic antidepressants and tetracyclic antidepressants
  183. Unexplained weight loss
  184. Vagus nerve stimulation
  185. Valerian: A safe and effective herbal sleep aid?
  186. Vascular dementia
  187. Video: Alzheimer's drug shows early promise
  188. Video: Vagus nerve stimulation
  189. Vitamin B-12 and depression
  190. What are opioids and why are they dangerous?
  191. What are the signs and symptoms of hidradenitis suppurativa?
  192. Wilson's disease
  193. Young-onset Alzheimer's