Psychology › Therapy & treatment › Psychiatric medicine: drugs and brain treatments
SSRI antidepressants (e.g., Prozac)
Prozac approved 1987· Therapy or method
Well replicatedStrong, repeated evidence.
Antidepressants such as Prozac, Zoloft and Lexapro that block serotonin's reabsorption, leaving more of it active between nerve cells.
See it on the Psychology map →What it says
Eli Lilly's fluoxetine (Prozac), approved by the FDA in December 1987, became the first blockbuster SSRI; sertraline, paroxetine, citalopram and escitalopram followed. They were safer in overdose and easier to tolerate than older antidepressants. They are used for depression, anxiety disorders, OCD and PTSD. Benefits usually appear after two to six weeks. Common side effects include nausea, sleep changes and sexual problems; stopping suddenly can cause withdrawal-like symptoms, so doses are normally tapered under medical supervision.
Why it matters
They made depression treatment routine in primary care, popularized the view of depression as a medical illness, and are taken by tens of millions of Americans.
The evidence
Status: well replicated, but effects are modest. Hundreds of placebo-controlled trials, FDA review files including unpublished trials, and national prescribing data; the benefit over placebo is often clearer in severe depression.
Open questions
Why they take weeks to work when serotonin rises within hours, why some people respond and others do not, and how common lasting withdrawal symptoms are.
Connections (4)
▸SSRI antidepressants (e.g., Prozac) boost signaling of SerotoninWell replicated
The connection
After a nerve cell releases serotonin, a transporter pump normally pulls it back in. SSRIs block that pump, so serotonin lingers between cells and its signal strengthens. Over weeks the brain adjusts its receptors in response, which may be what actually lifts mood.
Who showed it and when
Designed by drug companies in the 1970s; at Eli Lilly, Bryan Molloy, David Wong and Ray Fuller created fluoxetine in 1972.
The evidence
Lab studies confirm SSRIs bind the serotonin transporter, and PET scans show about 80 percent of transporters blocked at standard doses.
Open questions
A 2022 review led by Joanna Moncrieff found no consistent evidence that low serotonin causes depression, so SSRIs may help by other routes, such as boosting brain plasticity.
▸SSRI antidepressants (e.g., Prozac) are among the most prescribed drugs in Psychiatric medicine: drugs and brain treatmentsWell replicated
The connection
SSRIs were safer and simpler to prescribe than the older tricyclic antidepressants, which could be fatal in overdose. Family doctors began prescribing them widely, and they became a pillar of psychiatric medicine for depression, anxiety, OCD and PTSD.
Who showed it and when
From Prozac's 1987 US approval; US antidepressant use rose from roughly 2 to 3 percent of people in 1988–94 to about 13 percent of adults in 2015–18.
The evidence
CDC national health surveys track use, and sertraline and escitalopram rank among the most prescribed drugs in the US.
Open questions
Critics argue they are overprescribed for mild distress, where benefit over placebo is small; others note many people with depression still go untreated.
▸The placebo effect accounts for much of the benefit of SSRI antidepressants (e.g., Prozac)Mixed evidence
The connection
In antidepressant trials, people on placebo improve a lot: by Irving Kirsch's estimate, placebo groups achieve about 80 percent of the drug groups' improvement. So much of the benefit patients notice on SSRIs reflects natural recovery, expectation and care, with the drug adding a smaller extra effect.
Who showed it and when
Irving Kirsch and Guy Sapirstein raised the issue in 1998; Kirsch's 2008 analysis of FDA data on four newer antidepressants drew wide attention.
How solid is it?
FDA files, including unpublished trials, show an average drug-placebo gap of about 2 points on a 52-point depression scale; Cipriani's 2018 meta-analysis confirmed small but real effects.
Open questions
Averages can hide people who benefit greatly; researchers also dispute whether a 2-point gap matters clinically and whether side effects let patients guess they got the drug.
▸SSRI antidepressants (e.g., Prozac) modestly relieve Depression and mood disordersWell replicated
The connection
SSRIs relieve depression for many people, usually over two to six weeks, with benefits most visible in moderate to severe cases. On average the gain over placebo is modest, but some individuals respond strongly. Combining medication with talk therapy often works better than either alone.
Who showed it and when
Tested in hundreds of trials since the 1980s; the large US STAR*D study (2001–2006) followed real-world patients through several treatment steps.
The evidence
Andrea Cipriani's 2018 meta-analysis of 522 trials and about 116,000 patients found all 21 antidepressants studied beat placebo for acute depression.
Open questions
Whether average effects are meaningful in mild depression, why responses vary so much, and how STAR*D's reported remission rates hold up after a 2023 reanalysis.