free · from the FDA record · 33 of 37 medications state a trial length
How long were psychiatric medications tested before approval?
for the antidepressants below, the trials that earned FDA approval ran 4 to 12 weeks — most of them six to eight. every row here is the pivotal-trial record from the medication's own label and Drugs@FDA: how long, how many people, compared against what, and the application number so you can check it. this is what approval rested on. it is not evidence about years of use, and the page says so wherever that matters.
the short version
- an approval trial answers one question: does the drug beat placebo on a symptom scale over an acute episode. six to eight weeks is enough to measure that.
- what it cannot answer is what happens over years. that evidence, where it exists, comes from relapse-prevention extension studies, post-marketing reports, and observational data — each medication page walks through what its label actually says before you stop or change a dose.
- where the public record does not state a number, the cell below says so. nothing is estimated.
antidepressants
| medication | approved | approved for | trial length | people | compared against | application |
|---|---|---|---|---|---|---|
| sertraline | 1991 | major depressive disorder in adults | 6 and 8 weeks | not stated | Placebo and amitriptyline | NDA 019839 |
| fluoxetine | 1987 | major depressive disorder, acute and maintenance treatment | 5 and 6 weeks (acute adult trials) | not stated | Placebo | NDA 018936 |
| paroxetine | 1992 | major depressive disorder in adults | 6 weeks | not stated | Placebo | NDA 020031 |
| citalopram | 1998 | major depressive disorder in adults | 4 to 6 weeks | 1,063 patients on citalopram in the pooled placebo-controlled trials | Placebo | NDA 020822 |
| escitalopram | 2002 | major depressive disorder in adults | 8 weeks | 715 patients on escitalopram in the placebo-controlled trials | Placebo; citalopram as an active comparator in two studies | NDA 021323 |
| venlafaxine | 1997 | major depressive disorder in adults; indications for generalized anxiety disorder, social anxiety disorder, and panic disorder were added later | 8 and 12 weeks | 705 patients on the extended-release capsules across MDD studies | Placebo | NDA 020699 |
| desvenlafaxine | 2008 | the treatment of adults with major depressive disorder | 8 weeks | 1,834 patients on desvenlafaxine, 1,116 on placebo | Placebo | NDA 021992 |
| duloxetine | 2004 | major depressive disorder in adults; indications for generalized anxiety disorder, diabetic peripheral neuropathic pain, fibromyalgia, and chronic musculoskeletal pain were added later | 8 to 9 weeks | 3,779 patients on duloxetine across placebo-controlled MDD trials | Placebo | NDA 021427 |
| bupropion | 1996 | the treatment of major depressive disorder; this anchor is the 1996 sustained-release formulation, whose efficacy rests on trials of the earlier immediate-release form | 4 to 6 weeks | Drug arms of 34 to 110 patients | Placebo | NDA 020358 |
| mirtazapine | 1996 | the treatment of major depressive disorder in adults | 6 weeks | 453 patients on mirtazapine, 361 on placebo (pooled U.S. 6-week trials) | Placebo | NDA 020415 |
| trazodone | 1981 | the treatment of major depressive disorder in adults | not stated in the public record | 142 inpatients and 157 outpatients on trazodone in the controlled studies | Placebo | NDA 018207 |
| vortioxetine | 2013 | major depressive disorder in adults | 6 to 8 weeks | 2,616 patients on vortioxetine in the short-term studies | Placebo | NDA 204447 |
| esketamine | 2019 | treatment-resistant depression in adults, in conjunction with an oral antidepressant; the monotherapy option and the indication for depressive symptoms in major depressive disorder with acute suicidal ideation or behavior were added later | 4 weeks | 114 on esketamine vs 109 on placebo spray | Placebo nasal spray; both arms on a newly initiated oral antidepressant | NDA 211243 |
antipsychotics
| medication | approved | approved for | trial length | people | compared against | application |
|---|---|---|---|---|---|---|
| aripiprazole | 2002 | schizophrenia, and acute manic and mixed episodes associated with bipolar I disorder | 4 to 6 weeks | 367 to 420 patients per positive trial | Placebo; risperidone or haloperidol arms in three trials | NDA 021436 |
| olanzapine | 1996 | treatment of schizophrenia; the 1996 approval covered adults, with the bipolar I disorder and adolescent indications added later | 6 weeks (acute trials) | 149, 253, and 326 patients | Placebo; haloperidol arm in one trial | NDA 020592 |
| quetiapine | 1997 | schizophrenia | 6 weeks | 286 to 618 patients per trial | Placebo in two trials; dose comparison in one | NDA 020639 |
| risperidone | 1993 | schizophrenia in adults | 4 to 8 weeks | 160 to 1,356 patients per trial | Placebo in three trials; dose comparison in one | NDA 020272 |
| lurasidone | 2010 | treatment of schizophrenia; the 2010 approval was followed later by the adolescent and bipolar-depression indications | 6 weeks | 145 to 489 patients per study | Placebo; olanzapine or quetiapine XR in two studies | NDA 200603 |
| ziprasidone | 2001 | schizophrenia; acute bipolar mania | 4 and 6 weeks (short-term trials) | 139 to 419 patients per short-term trial | Placebo; haloperidol arm in one trial | NDA 020825 |
mood stabilizers
| medication | approved | approved for | trial length | people | compared against | application |
|---|---|---|---|---|---|---|
| lithium | 1970 | acute manic and mixed episodes of bipolar I disorder, and maintenance treatment, in patients 7 years and older; the 1970 approval predates by decades the pediatric trial that today's label describes | 8 weeks | 81 patients aged 7 to 17 | Placebo | NDA 016782 |
| lamotrigine | 2003 | maintenance treatment of bipolar I disorder to delay the time to occurrence of mood episodes (depression, mania, hypomania, mixed episodes) in patients treated for acute mood episodes with standard therapy; the epilepsy indications came first, in 1994 | Up to 18 months | 404 and 171 patients in the 2 trials | Placebo | NDA 020241 SUPPL-17 |
benzodiazepines and other anxiolytics
| medication | approved | approved for | trial length | people | compared against | application |
|---|---|---|---|---|---|---|
| alprazolam | 1981 | the acute treatment of generalized anxiety disorder and the treatment of panic disorder, with or without agoraphobia, in adults | 4 weeks (anxiety); up to 10 weeks (panic) | 565 patients on alprazolam vs 505 on placebo (anxiety trials) | Placebo | NDA 018276 |
| clonazepam | 1975 | seizure disorders (Lennox-Gastaut syndrome, akinetic and myoclonic seizures, and absence seizures unresponsive to succinimides); the panic disorder indication was added later | 6 to 9 weeks | 574 patients on clonazepam vs 294 on placebo | Placebo | NDA 017533 |
| diazepam | 1963 | the management of anxiety disorders or the short-term relief of the symptoms of anxiety; the label also covers acute alcohol withdrawal, skeletal muscle spasm, and adjunctive use in convulsive disorders | not stated in the public record | not stated | not stated | NDA 013263 |
| lorazepam | 1977 | the management of anxiety disorders or the short-term relief of the symptoms of anxiety or anxiety associated with depressive symptoms | not stated in the public record | About 3,500 patients in the anxiety sample | not stated | NDA 017794 |
| buspirone | 1986 | the management of anxiety disorders or the short-term relief of the symptoms of anxiety | 3 to 4 weeks | About 2,200 patients in the efficacy trials | Placebo | NDA 018731 |
| hydroxyzine | 1956 | symptomatic relief of anxiety and tension associated with psychoneurosis, and as an adjunct in organic disease states in which anxiety is manifested; the label also covers pruritus from allergic conditions and pre- and post-anesthetic sedation | not stated in the public record | not stated | not stated | NDA 010485 |
ADHD medications
| medication | approved | approved for | trial length | people | compared against | application |
|---|---|---|---|---|---|---|
| amphetamine | 2001 | the treatment of attention deficit hyperactivity disorder (ADHD) in adults and pediatric patients 6 years and older | 3 to 4 weeks | 584 children, 327 adolescents, 255 adults | Placebo | NDA 021303 |
| lisdexamfetamine | 2007 | the treatment of attention deficit hyperactivity disorder (ADHD), initially in children aged 6 to 12; the adolescent, adult, and binge eating disorder indications were added later | 4 weeks (1 week per treatment in the crossover studies) | 290 children in the parallel-group trial | Placebo; Adderall XR in one classroom study | NDA 021977 |
| methylphenidate | 2000 | the treatment of attention deficit hyperactivity disorder (ADHD); the current label covers patients aged 6 to 65 years old | 1 to 7 weeks | 416 children, 177 adolescents, 627 adults | Placebo and immediate-release methylphenidate | NDA 021121 |
| atomoxetine | 2002 | the treatment of attention-deficit/hyperactivity disorder (ADHD) in adults and pediatric patients 6 years of age and older | 6 to 10 weeks | 1,613 pediatric patients and 541 adults received atomoxetine in acute placebo-controlled studies | Placebo; methylphenidate in two pediatric studies | NDA 021411 |
| guanfacine | 2009 | the treatment of attention deficit hyperactivity disorder (ADHD) in children and adolescents 6 to 17, as monotherapy and as adjunctive therapy to stimulant medications | 5 to 8 weeks | 345 and 324 in the fixed-dose trials | Placebo | NDA 022037 |
sleep medications
| medication | approved | approved for | trial length | people | compared against | application |
|---|---|---|---|---|---|---|
| zolpidem | 1992 | the short-term treatment of insomnia characterized by difficulties with sleep initiation | 1 night to 5 weeks | 35 to 462 patients per trial | Placebo | NDA 019908 |
| temazepam | 1981 | the short-term treatment of insomnia (generally 7 to 10 days) | 2 weeks | 1,076 patients on temazepam vs 783 on placebo | Placebo | NDA 018163 |
other
| medication | approved | approved for | trial length | people | compared against | application |
|---|---|---|---|---|---|---|
| buprenorphine | 2010 | treatment of opioid dependence, as part of a complete treatment plan that includes counseling and psychosocial support (buprenorphine/naloxone sublingual film) | 4 and 16 weeks (safety studies) | Over 3000 opioid-dependent subjects | Placebo, in the 4-week tablet study | NDA 022410 |
| gabapentin | 1993 | adjunctive therapy for partial-onset seizures in adults and pediatric patients 3 years and older with epilepsy, and management of postherpetic neuralgia in adults; the label lists no psychiatric indication | 12 weeks | 705 patients aged 12 and older, plus 247 children | Placebo, added to existing antiepileptic drugs | NDA 020235 |
| modafinil | 1998 | improving wakefulness in adult patients with excessive sleepiness associated with narcolepsy; the obstructive sleep apnea and shift work disorder indications were added later | 9 weeks | 558 patients | Placebo | NDA 020717 |
straight answers
How long were antidepressants tested in clinical trials before approval?
For the 12 antidepressants on this page whose FDA record states a trial length, the placebo-controlled trials that earned approval ran 4 to 12 weeks, with most between six and eight weeks. That is the acute-treatment trial the label reports. Longer relapse-prevention studies exist for some drugs and are described on each medication's own page; none of the approval trials listed here ran for years.
What are the long-term effects of taking an antidepressant like Zoloft for 10 years?
The approval record cannot answer that, and this page does not pretend it can. The trials that approved sertraline (Zoloft) ran six and eight weeks; no drug on this page was approved on a decade-long controlled trial. What exists for longer use is relapse-prevention extension studies, post-marketing adverse-event reports (FAERS), and observational data — different kinds of evidence with different limits. Each medication page lists what its label says under "Before you stop or change your dose", and the decision about staying on a medication belongs with you and your prescriber, not a table.
Where do these numbers come from?
Every row is hand-curated from the medication's FDA label (the Clinical Studies section on DailyMed) and Drugs@FDA, and carries the application number so you can pull the approval documents yourself. Where the public record does not state a figure, the cell says so rather than filling it in. Nothing here is estimated or modelled.
Why do trials run only a few weeks?
Because the regulatory question is whether the drug beats placebo on a symptom scale over an acute episode, and that can be measured in six to eight weeks. It is a reasonable way to test efficacy and a poor way to learn about years of use — which is why the label, the FAERS reports, and the relapse-prevention studies all have to be read together. This page shows the first of those; the medication pages show the rest.
related
how long the trials in our evidence library ran — a different dataset: the 72 randomised trials we score, not the approval record · side-effect rates, drug vs placebo from the same labels · the medication library with each drug's approval walked through step by step · how we score evidence. veisund is free peer support and public-record information — not medical advice. in crisis in the US, call or text 988.