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Selective serotonin reuptake inhibitors (SSRIs) are a class of antidepressant medications prescribed for the treatment of a range of psychiatric disorders. They are most often used for depression, but may also help manage symptoms of anxiety and anxiety-related disorders.

What Are SSRIs?


It is believed that SSRIs work by increasing the amount of the neurotransmitter serotonin in the brain, though their exact mechanism of action remains unknown. Serotonin is thought to be low in individuals with major depression and anxiety disorders. Having more serotonin available in the nerve synapse makes it easier to transmit the messages between cells that contribute to a person’s mood, appetite, regular biorhythms, and overall well-being.

The first major SSRI to be introduced to the general public was fluoxetine (more commonly known as Prozac) in the late '80s; Prozac remains one of the most popular SSRIs today. Serotonin-norepinephrine reuptake inhibitors (SNRIs or SSNRIs) increase levels of both serotonin and norepinephrine by delaying the reuptake of both neurotransmitters.

What conditions do SSRIs treat?

Although SSRIs are primarily used to treat depression, they can be helpful in reducing anxiety and related conditions. In some instances, they have also been used to treat impulse-related disorders like anorexia or trichotillomania (hair-pulling disorder)—though evidence of their efficacy for these disorders is mixed, and they are not a first-line treatment in many cases. They are also used to treat eating disorders.

What are some common types of SSRIs?

A few examples of popular SSRI antidepressants include sertraline (Zoloft), fluoxetine (Prozac, Sarafem), citalopram (Celexa), paroxetine (Paxil, Brisdelle, Pexeva), escitalopram (Lexapro), fluvoxamine (Luvox), and vilazodone (Viibryd).

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Risks and Side Effects of SSRIs

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Though the class of drugs was developed in the hopes of eliminating some of the unpleasant (and dangerous) side effects of their predecessors, certain side effects remain. Some, like an increased risk of suicidal ideation or cardiac arrest, are very serious, while others, like dry mouth or sexual dysfunction, can be troublesome, but are not life-threatening. Because of their side effects, however—as well as their inconsistent results in treating depression—they continue to generate controversy. Like most antidepressants, SSRIs appear to be most effective when used in combination with cognitive-behavioral therapy or other forms of therapy.

Do SSRIs cause sexual dysfunction?

Approximately 70 percent of people taking SSRIs will experience some form of sexual dysfunction, including the loss of orgasm. Even as SSRIs increase serotonin levels, they have a dampening effect on dopamine, which is responsible for the elation of falling in love. Patients should be aware of the potential for some SSRIs to wreak long-term havoc on their love lives.

Do SSRIs make you gain weight?

Taking antidepressants has been linked to significant weight gain. Women and individuals who are already overweight are more likely to experience this undesirable side effect. Paxil and Lexapro are known to contribute to weight gain; switching prescriptions may be an option for some patients.  

How Effective Are SSRIs?


Depression is a notoriously difficult illness to treat. Talk therapy, while undeniably helpful, is often not enough to fully eradicate symptoms or ward off relapse. A large meta-analysis published in The Lancet in 2018 found that, overall, all SSRIs and SNRIs were more effective than placebo in treating adults with major depression. However, many well-known SSRIs are ineffective for as many as 30 percent of people who try them.

Patients who are prescribed an SSRI that doesn’t appear to manage their symptoms well often feel discouraged or unwilling to try another option, further complicating their treatment prospects. It’s important to remember that any antidepressant regimen takes weeks or months to start working on symptoms. And while some forms of depression do appear to resist antidepressant treatment, in many cases, it may be necessary to try two, three, or four medications before finding one that works. There is evidence that in the near future, psychiatrists will be able to use specific biomarkers to more effectively pair patients with specific SSRIs and other psychotropics, thus reducing the trial and error that now characterizes the process.

How do you know if an SSRI is working?

Since symptoms targeted by SSRIs are primarily psychological, changes will likely be subtle and may not progress in a linear way. In cases of depression, non-mood-related symptoms—such as insomnia or mental slowness—may start to improve first, often within three weeks of beginning treatment. A 2018 research review found that most patients who eventually saw improvements in mood first reported gains in cognition. As a result, changes in cognition may be one way to better predict whether an antidepressant will work for a patient.

How long does it take to start seeing improvement on an SSRI?

After approximately four to six weeks of treatment, patients who are responding to SSRIs will likely notice that they have more energy, are less anxious, and feel less hopeless about the future. If a patient has not shown such improvement after six weeks, it’s likely that their doctor will recommend trying another antidepressant.

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