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Treatment terms

Antidepressant

Shariq Refai, MD, MBA, board-certified psychiatrist and the reviewer of this article.

Reviewed by Shariq Refai, MD, MBA·Updated March 15, 2026·About 3 minutes

About this term

Quick definition
A medication used to treat depression. Common classes include SSRIs, SNRIs, atypical antidepressants such as bupropion and mirtazapine, tricyclics, and MAOIs.
Full clinical definition
Antidepressants are a heterogeneous group of medications that have demonstrated efficacy in treating major depressive disorder and several anxiety, trauma, and obsessive-compulsive disorders. They work through different neurotransmitter systems, including serotonin, norepinephrine, and dopamine. Specific receptor and reuptake effects vary by class and by individual drug.

Common classes used in depression.

ClassExamplesCommon reasons to choose
SSRISertraline, escitalopram, fluoxetine, paroxetine, citalopramMost common first-line; well-tolerated profile
SNRIVenlafaxine, duloxetine, desvenlafaxineSometimes chosen when pain is part of the picture
AtypicalBupropionLow motivation, fatigue; no sexual side effects
AtypicalMirtazapineSevere sleep and appetite disruption
TricyclicNortriptyline, amitriptylineOlder class; sometimes chosen by experienced clinicians
MAOIPhenelzine, tranylcypromineReserved cases; requires dietary precautions
MultimodalVortioxetineSome cognitive symptoms; expensive
How they work, briefly
SSRIs and SNRIs block the reuptake of serotonin (and norepinephrine for SNRIs), increasing the availability of these signaling molecules in the brain. Bupropion affects dopamine and norepinephrine. Mirtazapine works on different serotonin receptors and on alpha-2 adrenergic receptors. The relationship between these chemical effects and clinical improvement is more complicated than the early "chemical imbalance" framing suggested, and is the subject of ongoing research.
Timeline
Most people start to notice changes in two to six weeks. Sleep, appetite, and energy often shift before mood does. Full effects often take eight to twelve weeks. The first medication tried is not always the right one. About one in three people reach full remission on the first antidepressant tried, and roughly half show a meaningful response. With sequential adjustments across up to four steps, cumulative remission rises further, though reanalyses with stricter outcome criteria report lower rates than the original report (Pigott, 2010). The number tried matters less than the willingness to keep adjusting.
Common side effects
Vary by class. Common ones across antidepressants include nausea, headache, sleep changes, sexual side effects, and a temporary increase in anxiety in the first weeks. Most settle. New or worsening suicidal thoughts in the first weeks of starting any antidepressant, especially in younger people, are a reason to call a prescriber the same day.
What this glossary entry is not
It is not a prescription, a recommendation, or a substitute for a clinical evaluation. Specific medication decisions belong with a clinician.
Related terms
SSRI. SNRI. Bupropion. Medication management. Psychiatric evaluation.
Related articles
Treatment. Antidepressant comparison. Stopping antidepressants. Major depressive disorder.

Sources

  • American Psychiatric Association. Practice Guideline for the Treatment of Patients with Major Depressive Disorder.
  • NICE Guideline NG222.
  • Cipriani A, et al. Comparative efficacy and acceptability of 21 antidepressant drugs for the acute treatment of adults with major depressive disorder: a systematic review and network meta-analysis. Lancet. 2018.

Frequently asked questions

How long do antidepressants take to work?
Most people start to notice changes in two to six weeks, with sleep, appetite, and energy often shifting before mood does. Full effects often take eight to twelve weeks. The first medication tried is not always the right one.
What is the success rate of the first antidepressant?
About one in three people reach remission on the first medication tried, and roughly half show a meaningful response (STAR*D). Most patients need a change in dose, a switch, or an addition. That is normal and built into how we plan treatment.
Are antidepressants addictive?
Antidepressants are not addictive in the way that opioids or benzodiazepines are. They do not produce a high, and people do not develop cravings. Stopping abruptly can cause discontinuation symptoms (flu-like feelings, brain zaps, mood changes), which is why a taper supervised by a prescriber is the standard approach.
Will antidepressants change who I am?
When they work, antidepressants reduce the symptoms that have been pushing on you. Most people describe themselves as more like themselves, not less. If you feel emotionally flat or unlike yourself on a medication, that is a reason to talk to the prescriber about the dose or a different medication.
Do I have to take an antidepressant forever?
After a first episode, most clinicians continue antidepressants for six to twelve months after symptoms resolve, then reassess. After multiple episodes, longer maintenance is often recommended. The decision is individual and is made with a prescriber.
What is the FDA boxed warning?
All antidepressants carry an FDA boxed warning for increased risk of suicidal thoughts in children, adolescents, and young adults up to age 25, especially in the first weeks of starting or changing a medication. Any new or worsening suicidal thoughts during this period are a reason to call a prescriber the same day.

Last reviewed March 15, 2026.

Every clinical page on DepressionResource.org is written in plain language, dated, and reviewed by a board-certified psychiatrist against current clinical guidelines. See our editorial standards and medical review process.