If you’ve been prescribed an antidepressant, or you’re weighing a switch, the question of SSRI vs SNRI often comes up quickly. Both are among the most commonly prescribed medications for depression and anxiety, and both can work well. They differ in how they act on brain chemistry, in their side-effect profiles, and in when a psychiatrist might reach for one over the other. This guide explains the difference, what research says about switching, and how the choice gets made.
What Is the Difference Between SSRIs and SNRIs?
The difference between SSRIs and SNRIs is that SSRIs block the reuptake of serotonin, while SNRIs block the reuptake of both serotonin and norepinephrine, leaving more of each available to nerve cells. Common SSRIs include sertraline, escitalopram, citalopram, fluoxetine, and paroxetine. Common SNRIs include venlafaxine, desvenlafaxine, duloxetine, and levomilnacipran.
The National Institute of Mental Health lists SSRIs and SNRIs among the usual medication options for depression, and notes that antidepressants can take weeks to work and that some people need to try more than one.
| SSRIs | SNRIs | |
|---|---|---|
| How they work | Block serotonin reuptake | Block serotonin and norepinephrine reuptake |
| Examples | Sertraline, escitalopram, citalopram, fluoxetine, paroxetine | Venlafaxine, desvenlafaxine, duloxetine, levomilnacipran |
| Common side effects | Nausea, headache, sleep changes, sexual side effects | Similar, plus sweating and possible blood pressure increases |
| Often considered when | Starting treatment for depression or anxiety | An SSRI hasn’t helped enough, or certain pain conditions are present |
How Serotonin and Norepinephrine Affect Mood
Serotonin and norepinephrine are chemical messengers that help regulate mood, sleep, appetite, energy, attention, and the body’s stress response, and antidepressants that affect them can ease many symptoms of depression and anxiety. Serotonin is closely tied to mood, worry, and sleep. Norepinephrine plays a larger role in alertness, energy, and focus.
That’s part of why an SNRI is sometimes considered when low energy or poor concentration are prominent, or when someone also has certain chronic pain conditions, since duloxetine, for example, is also used for some pain disorders. Still, depression isn’t simply a chemical shortage, and no one can predict from symptoms alone which medication will work best for a specific person.
The better antidepressant is usually the one that fits your history, your symptoms, and the side effects you can live with.
SSRI vs SNRI: What the Research Shows
On average, SSRIs and SNRIs work about equally well for depression, and differences between individual antidepressants are modest compared with the difference between any antidepressant and placebo. A large network meta-analysis of 522 trials with 116,477 participants found that all 21 antidepressants studied were more effective than placebo, with only modest differences among them.
Head-to-head switching data point the same way. In the STAR*D trial, 727 adults whose depression hadn’t remitted on the SSRI citalopram were randomly assigned to switch to bupropion, the SSRI sertraline, or the SNRI venlafaxine. About one in four reached remission after switching, and the three options didn’t differ significantly in outcomes, tolerability, or side effects.
Share reaching remission (HRSD-17) after switching to each medication. Differences were not statistically significant.
Share whose symptoms improved by at least 50% (QIDS-SR-16) after switching.
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Common SNRI Side Effects Compared With SSRIs
Common SNRI side effects overlap with SSRI side effects, including nausea, headache, sleep changes, and sexual side effects, but SNRIs are also more likely to cause sweating, a faster heart rate, and increases in blood pressure. Because of that, blood pressure checks are part of monitoring on some SNRIs, especially at higher doses.
Both classes can cause discontinuation symptoms if stopped suddenly, and some SNRIs, venlafaxine in particular, are known for more noticeable symptoms when a dose is missed. Many early side effects of either class ease within the first few weeks. If a side effect isn’t fading, or it affects your quality of life, tell your psychiatrist. Adjusting the dose, the timing, or the medication can often help.
Switching From an SSRI to an SNRI
Switching from an SSRI to an SNRI is a common next step when an SSRI hasn’t helped enough after an adequate trial or causes side effects you can’t tolerate, and it’s done with a plan to limit overlap and withdrawal. Your psychiatrist will decide whether to taper one medication before starting the other, cross-taper gradually, or make a direct switch, depending on the drugs and doses involved.
- Review the first trial. Confirm the dose and duration were adequate and note any partial benefit.
- Weigh side effects. Consider which side effects you had and which you most want to avoid.
- Plan the transition. Your psychiatrist chooses a taper, cross-taper, or direct switch for your medications.
- Watch the first weeks. Report new side effects, blood pressure changes, or withdrawal-like symptoms.
- Measure the result. Track symptoms with a rating scale to judge the new medication fairly.
Switching isn’t the only option. If an SSRI helped partway, raising the dose or adding a second medication may make more sense than starting over. And if two adequate trials haven’t worked, our guide to treatment-resistant depression explains why a fuller re-evaluation is the next step. Our timeline of how long antidepressants take to work can help you judge whether a trial has been long enough.
The first antidepressant fell short
An SSRI helped a little, or not at all, or the side effects were hard to live with.
A reasoned next choice
A review of your history, symptoms, and health to pick between an SSRI, an SNRI, or another option.
A medication that fits
Relief with side effects you can accept, tracked with rating scales over time.
Dr. Gabriella Farkas, MD PhD
Board-certified adult psychiatrist with a PhD in neuroscience and pharmaceutical research experience. Dr. Farkas explains how each medication works and why it fits your situation.
About Dr. Farkas →How a Psychiatrist Chooses Between an SSRI and an SNRI
A psychiatrist chooses between an SSRI and an SNRI by weighing your symptoms, past responses, side-effect history, other health conditions, current medications, and personal priorities. There’s no single right answer for everyone, which is why the choice is a conversation rather than a formula.
Factors that often come up include blood pressure, heart health, chronic pain, sleep, sexual side effects, weight concerns, how reliably you can take daily doses, and interactions with other medications. Family history of good response to a particular medication can matter too. A comprehensive adult psychiatric evaluation brings all of that together before a recommendation is made. If you’re having thoughts of suicide, call or text 988 in the US.
Key Terms
- SSRI
- Selective serotonin reuptake inhibitor, an antidepressant that increases serotonin signaling by blocking its reuptake.
- SNRI
- Serotonin-norepinephrine reuptake inhibitor, an antidepressant that blocks the reuptake of both serotonin and norepinephrine.
- Cross-taper
- Gradually lowering one medication while gradually starting another to reduce side effects and withdrawal.
- Discontinuation symptoms
- Temporary symptoms such as dizziness, nausea, or irritability that can occur when an antidepressant is reduced or stopped.
Common Questions About SSRIs and SNRIs
Are SNRIs stronger than SSRIs?
SNRIs aren't generally stronger than SSRIs; on average, research shows the two classes work about equally well for depression, with only modest differences among individual antidepressants. What differs is how each person responds. Side effects also differ. Your history matters most. A psychiatrist can weigh the options with you. Past responses often guide the choice.
What is the main difference between an SSRI and an SNRI?
The main difference is that SSRIs act mainly on serotonin, while SNRIs act on both serotonin and norepinephrine, which can affect energy, alertness, and some types of pain. Their side effects overlap. SNRIs can raise blood pressure. Both take weeks to work. Neither is right for everyone. Your psychiatrist can explain which fits you.
Do SNRIs cause more side effects than SSRIs?
SNRIs share many side effects with SSRIs, such as nausea and sexual side effects, and may also cause sweating, a faster heart rate, or higher blood pressure. Tolerability varies by person. In STAR*D, switch options didn't differ significantly in tolerability. Many early side effects fade. Report any that don't. Blood pressure checks may be part of monitoring.
Can I switch from an SSRI to an SNRI on my own?
No, you shouldn't switch from an SSRI to an SNRI on your own, because the change needs a plan to limit overlap, withdrawal, and side effects. Your psychiatrist will choose the approach. Options include tapering or cross-tapering. Doses matter. Follow-up helps catch problems early. Stopping suddenly can cause discontinuation symptoms.
How long should I try an SSRI before switching?
Many psychiatrists reassess an SSRI after several weeks at an adequate dose, and little or no improvement by around four to six weeks is often a reason to discuss a change. Partial improvement may justify a dose increase. Experts don't agree on one exact cutoff. Rating scales help. Decide together.
Are SNRIs better for anxiety?
SNRIs aren't necessarily better for anxiety than SSRIs; both classes are commonly used for anxiety disorders, and the choice depends on your symptoms, history, and side effects. Some people respond better to one. Others do well on either. Therapy also helps many people. Your psychiatrist can help you decide. Side-effect history often tips the balance.
Can I get an antidepressant review by telehealth?
Yes, Dr. Farkas reviews antidepressant treatment by secure telehealth for adults in South Carolina and New York, including whether an SSRI, an SNRI, or another option fits best. Bring your medication history. Note side effects you've had. You'll need a private space. Prescriptions can be sent to your pharmacy. Follow-ups use the same platform.
The right antidepressant is the one that fits you.
A thoughtful review of your options.
Sources
- Rush AJ, Trivedi MH, Wisniewski SR, et al. “Bupropion-SR, sertraline, or venlafaxine-XR after failure of SSRIs for depression.” New England Journal of Medicine, 2006;354(12):1231–1242. https://www.nejm.org/doi/full/10.1056/NEJMoa052963
- Cipriani A, Furukawa TA, Salanti G, 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.” The Lancet, 2018;391(10128):1357–1366. https://boris.unibe.ch/112281
- National Institute of Mental Health. “Depression.” NIMH Health Topics. https://www.nimh.nih.gov/health/topics/depression
Educational content only. This article does not constitute medical advice and does not establish a doctor-patient relationship. If you are in crisis, call or text 988 (Suicide & Crisis Lifeline) or call 911. Treatment decisions should be made with a qualified clinician familiar with your circumstances. Last reviewed: August 2026.