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What Are SSRIs?

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 disorders, including obsessive-compulsive disorder, post-traumatic stress disorder, or social anxiety disorder. 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

Though their exact mechanism of action remains unknown, it is believed that SSRIs work by increasing the amount of the neurotransmitter serotonin in the brain; serotonin is thought to be low in individuals with major depression and anxiety disorders. 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 reuptake of both neurotransmitters.

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.

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, areineffective for as many as 30 percent of people who try them.

Patients who are prescribed an SSRI that doesn’t appear to manage 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.

Successful Responses to SSRIs

Determining if SSRIs are working can be a time-consuming and frustrating process. It’s critical, then, to know what a successful response might look like. 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.

Mood changes often occur last. 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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