What are SSRIs?

Selective serotonin reuptake inhibitors (SSRIs) are a class of antidepressants that are used in the treatment of clinical depression. These agents are also useful in several other mental health conditions such as anxiety disorder, obsessive compulsive disorder, panic disorder and some phobias such as social phobia and agoraphobia (fear of open spaces).

Examples of SSRIs

Some examples of commonly used SSRIs include:

  • Fluoxetine (prozac)
  • Sertraline
  • Fluvoxamine
  • Paroxetine
  • Citalopram
  • Escitalopram

Mechanism of action

SSRIs increase the serotonin level in the brain by preventing it's reuptake by the presynaptic neurons, meaning the hormone instead remains available to bind to postsynaptic neurons and exert its mood enhancing effects. Many experts believe that low serotonin levels are a cause depression.

Increased serotonin levels due to SSRI therapy has proved beneficial in the treatment of individuals with depression. SSRIs are currently the mainstay of treatment for depression and are preferred over other classes of medications such as tricyclic antidepressants and monoamine-oxidase inhibitors because they are more effective and cause fewer side effects.

Side effects of SSRIs

Some of the side effects of SSRIs include:

  • Increase in suicidal thoughts and behaviors.
  • Anxiety, restlessness, agitation, aggressiveness and hostility
  • Sudden cessation of SSRIs can cause withdrawal syndrome
  • Nausea, vomiting, weight gain or loss, dry mouth, diarrhea and constipation
  • Loss of sleep or insomnia
  • Tremors
  • Headaches
  • Excessive sweating
  • Dizziness
  • Blurred vision
  • Loss of libido and erectile dysfunction

With time, many of the less serious side effects of SSRI therapy may improve. Those under the age of 25 years are more at risk of suicidal thoughts and self-harm behaviors with the use of SSRIs than other age group and this is an important side effect to look out for in young people with depression.


Usually, the lowest dose of the drug is prescribed at first. The dose may be gradually increased over time as side effects begin to improve. SSRIs start to take effect at around two to four weeks, when a patient starts to feel an improvement in their mood.

SSRIs must not be prescribed in the presence of certain other conditions such as pregnancy (unless the benefits outweigh the risks), kidney dysfunction or glaucoma.

Further Reading

Last Updated: Jun 10, 2023

Dr. Ananya Mandal

Written by

Dr. Ananya Mandal

Dr. Ananya Mandal is a doctor by profession, lecturer by vocation and a medical writer by passion. She specialized in Clinical Pharmacology after her bachelor's (MBBS). For her, health communication is not just writing complicated reviews for professionals but making medical knowledge understandable and available to the general public as well.


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  1. Tony Harewood Tony Harewood Australia says:

    As a recipient of 3 various SSRI's over each day, these details deserve the respect & complements of an ABI Survivor. My experienced Psychiatrist was fairly accurate with the initial prescriptions, with only minor adjustments needed.

The opinions expressed here are the views of the writer and do not necessarily reflect the views and opinions of News Medical.
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