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.
| Class | Examples | Common reasons to choose |
|---|---|---|
| SSRI | Sertraline, escitalopram, fluoxetine, paroxetine, citalopram | Most common first-line; well-tolerated profile |
| SNRI | Venlafaxine, duloxetine, desvenlafaxine | Sometimes chosen when pain is part of the picture |
| Atypical | Bupropion | Low motivation, fatigue; no sexual side effects |
| Atypical | Mirtazapine | Severe sleep and appetite disruption |
| Tricyclic | Nortriptyline, amitriptyline | Older class; sometimes chosen by experienced clinicians |
| MAOI | Phenelzine, tranylcypromine | Reserved cases; requires dietary precautions |
| Multimodal | Vortioxetine | Some 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 isn't 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 isn't
- It isn't 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.