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 and current health topics, like COVID-19, plus expertise on managing health.

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. After a flood, are food and medicines safe to use?
  5. Alzheimer's: New treatments
  6. Alzheimer's 101
  7. Understanding the difference between dementia types
  8. Alzheimer's disease
  9. Alzheimer's disease: Can exercise prevent memory loss?
  10. Alzheimer's drugs
  11. Alzheimer's genes
  12. Alzheimer's nose spray: New Alzheimer's treatment?
  13. Alzheimer's prevention: Does it exist?
  14. Alzheimer's stages
  15. Ambien: Is dependence a concern?
  16. Antidepressant withdrawal: Is there such a thing?
  17. Antidepressants and alcohol: What's the concern?
  18. Antidepressants and weight gain: What causes it?
  19. Antidepressants: Can they stop working?
  20. Antidepressants: Side effects
  21. Antidepressants: Selecting one that's right for you
  22. Antidepressants: Which cause the fewest sexual side effects?
  23. Antidepressants and pregnancy
  24. Atypical antidepressants
  25. Atypical depression
  26. Back pain
  27. Bedtime routines: Not just for babies
  28. Binge-eating disorder
  29. Blood Basics
  30. Borderline personality disorder
  31. Breastfeeding and medications
  32. Dr. Wallace Video
  33. Dr. Mark Truty (surgery, MN) better outcomes with chemo
  34. Parathyroid
  35. Can music help someone with Alzheimer's?
  36. Can zinc supplements help treat hidradenitis suppurativa?
  37. Can't sleep? Try daytime exercise
  38. Hidradenitis suppurativa wound care
  39. Celiac disease
  40. Chase away the winter blues
  41. Child abuse
  42. Chronic traumatic encephalopathy
  43. CJD - Creutzfeldt-Jakob Disease
  44. Clinical depression: What does that mean?
  45. Clinical trials for hidradenitis suppurativa
  46. Coconut oil: Can it cure hypothyroidism?
  47. Coffee after dinner? Make it decaf
  48. Complete blood count (CBC)
  49. Complicated grief
  50. Compulsive sexual behavior
  51. Concussion
  52. Concussion in children
  53. Concussion Recovery
  54. Concussion Telemedicine
  55. Coping with the stress of hidradenitis suppurativa
  56. Coping with the emotional ups and downs of psoriatic arthritis
  57. COVID-19 and your mental health
  58. Creating a hidradenitis suppurativa care team
  59. Creutzfeldt-Jakob disease
  60. Cushing syndrome
  61. Cyclothymia (cyclothymic disorder)
  62. Delirium
  63. Depression and anxiety: Can I have both?
  64. Depression, anxiety and exercise
  65. Depression: Diagnosis is key
  66. Depression during pregnancy
  67. Depression in women: Understanding the gender gap
  68. Depression (major depressive disorder)
  69. Depression: Provide support, encouragement
  70. Depression: Supporting a family member or friend
  71. Diabetes and depression: Coping with the two conditions
  72. Diagnosing Alzheimer's
  73. Dissociative disorders
  74. Vitamin C and mood
  75. Drug addiction (substance use disorder)
  76. Electroconvulsive therapy (ECT)
  77. Fatigue
  78. Fibromyalgia
  79. Fibromyalgia and acupuncture
  80. Fibromyalgia: Linked to other health problems?
  81. HABIT program orientation
  82. Hangovers
  83. Hashimoto's disease
  84. Headache
  85. Hidradenitis suppurativa
  86. Hidradenitis suppurativa and biologics: Get the facts
  87. Hidradenitis suppurativa and diet: What's recommended?
  88. Hidradenitis suppurativa and sleep: How to get more zzz's
  89. Hidradenitis suppurativa: Tips for weight-loss success
  90. Hidradenitis suppurativa: What is it?
  91. Hidradenitis suppurativa: When does it appear?
  92. Hidradenitis suppurativa: Where can I find support?
  93. How opioid addiction occurs
  94. How to tell if a loved one is abusing opioids
  95. Hyperparathyroidism
  96. Hypoparathyroidism
  97. Hypothyroidism: Can calcium supplements interfere with treatment?
  98. Hypothyroidism diet
  99. Hypothyroidism and joint pain?
  100. Hypothyroidism: Should I take iodine supplements?
  101. Hypothyroidism symptoms: Can hypothyroidism cause eye problems?
  102. Hypothyroidism (underactive thyroid)
  103. Insomnia
  104. Insomnia: How do I stay asleep?
  105. Insomnia treatment: Cognitive behavioral therapy instead of sleeping pills
  106. Intervention: Help a loved one overcome addiction
  107. Is depression a factor in rheumatoid arthritis?
  108. Is fibromyalgia hereditary?
  109. Is the definition of Alzheimer's disease changing?
  110. Kratom for opioid withdrawal
  111. Lack of sleep: Can it make you sick?
  112. Living better with hidradenitis suppurativa
  113. Low blood pressure (hypotension)
  114. Male depression: Understanding the issues
  115. Managing Headaches
  116. Managing hidradenitis suppurativa: Early treatment is crucial
  117. Hidradenitis suppurativa-related health risks
  118. MAOIs and diet: Is it necessary to restrict tyramine?
  119. Marijuana and depression
  120. Mayo Clinic Minute: 3 tips to reduce your risk of Alzheimer's disease
  121. Mayo Clinic Minute: Alzheimer's disease risk and lifestyle
  122. Mayo Clinic Minute New definition of Alzheimer's changes
  123. Mayo Clinic Minute: Prevent migraines with magnetic stimulation
  124. Mayo Clinic Minute: Restless legs syndrome in kids
  125. Mayo Clinic Minute Weathering migraines
  126. Mayo Clinic Minute: Women and Alzheimer's Disease
  127. Medication overuse headaches
  128. Meditation
  129. Mediterranean diet recipes
  130. Memory loss: When to seek help
  131. Mental health: Overcoming the stigma of mental illness
  132. Mental health providers: Tips on finding one
  133. Mental health
  134. Mental illness
  135. Migraine
  136. What is a migraine? A Mayo Clinic expert explains
  137. Migraine medications and antidepressants
  138. Migraine FAQs
  139. Migraine treatment: Can antidepressants help?
  140. Infographic: Migraine Treatments: Botox & Nerve Blocking
  141. Migraines and gastrointestinal problems: Is there a link?
  142. Migraines and Vertigo
  143. Migraines: Are they triggered by weather changes?
  144. Alleviating migraine pain
  145. Mild cognitive impairment (MCI)
  146. Mindfulness exercises
  147. Monoamine oxidase inhibitors (MAOIs)
  148. Natural remedies for depression: Are they effective?
  149. Nervous breakdown: What does it mean?
  150. New Alzheimers Research
  151. Nicotine dependence
  152. Not tired? Don't go to bed
  153. Occipital nerve stimulation: Effective migraine treatment?
  154. Ocular migraine: When to seek help
  155. Oppositional defiant disorder (ODD)
  156. Pain and depression: Is there a link?
  157. Pancreatic cancer
  158. Pancreatic Cancer
  159. What is pancreatic cancer? A Mayo Clinic expert explains
  160. Infographic: Pancreatic Cancer: Minimally Invasive Surgery
  161. Pancreatic Cancer Survivor
  162. Infographic: Pancreatic Cancers-Whipple
  163. Perimenopause
  164. Pituitary tumors
  165. Polymyalgia rheumatica
  166. Premenstrual dysphoric disorder
  167. Premenstrual syndrome (PMS)
  168. Prescription drug abuse
  169. Prescription sleeping pills: What's right for you?
  170. Progressive supranuclear palsy
  171. Psychotherapy
  172. Reducing the discomfort of hidradenitis suppurativa: Self-care tips
  173. Restless legs syndrome
  174. Salt craving: A symptom of Addison's disease?
  175. Schizoaffective disorder
  176. Seasonal affective disorder (SAD)
  177. Seasonal affective disorder treatment: Choosing a light box
  178. Serotonin and norepinephrine reuptake inhibitors (SNRIs)
  179. Skip booze for better sleep
  180. Sleep disorders
  181. Sleep tips
  182. Soy: Does it worsen hypothyroidism?
  183. Staying active with hidradenitis suppurativa
  184. Stop your next migraine before it starts
  185. Stress symptoms
  186. Sundowning: Late-day confusion
  187. Support groups
  188. Surgery for hidradenitis suppurativa
  189. Symptom Checker
  190. Tapering off opioids: When and how
  191. Tinnitus and antidepressants
  192. Transcranial magnetic stimulation
  193. Traumatic brain injury
  194. Treating hidradenitis suppurativa: Explore your options
  195. Treating hidradenitis suppurativa with antibiotics and hormones
  196. Treatment-resistant depression
  197. Tricyclic antidepressants and tetracyclic antidepressants
  198. Unexplained weight loss
  199. Vagus nerve stimulation
  200. Valerian: A safe and effective herbal sleep aid?
  201. Vascular dementia
  202. Video: Alzheimer's drug shows early promise
  203. Video: Vagus nerve stimulation
  204. Vitamin B-12 and depression
  205. What are opioids and why are they dangerous?
  206. What are the signs and symptoms of hidradenitis suppurativa?
  207. What is reflexology?
  208. Wilson's disease
  209. Wilson's syndrome: An accepted medical diagnosis?
  210. Young-onset Alzheimer's