SSRI vs SNRI: Understanding How Antidepressants Work

Read Time: 7 Minutes
Written by:Marris Adikwu

Published On: November 6, 2020

Medically reviewed by: Bisma Anwar, MA, MSc, LMHC

Reviewed On: November 6, 2020

Updated On: November 1, 2023


For those struggling with depression and looking for pharmaceutical intervention — antidepressants — to manage their symptoms, it can be challenging to understand how various antidepressants work and which is the best fit. Regular visits to your provider may offer more information about the SSRIs, SNRIs, and NDRIs that can help you decide which is the best choice, but trying to remember the names of some drugs — as well as their function — can cause confusion, especially if you’re treating the same condition with different classes of medications.

Selective serotonin reuptake inhibitors (SSRIs) and serotonin and norepinephrine reuptake inhibitors (SNRIs) are two classes of antidepressants that are effective in treating depression and other conditions. However, there are important differences between these two types of reuptake inhibitors. If you’re looking to broaden your knowledge of medication options available to you, you can find out more about these two classes of antidepressants, and the different ways they both work.

Antidepressants and Your Brain Chemistry

Although antidepressants have been proven to be effective in improving depression symptoms, it’s still unclear how they exactly work. Yet, extensive research in this field has led experts to believe that these antidepressants affect certain brain circuits and chemicals known as neurotransmitters to transfer signals from one nerve cell in the brain to another.

Neurotransmitters are released from nerve endings, and they’re used by nerve cells to communicate with one another and their target tissues. In order to treat depression, panic disorder, anxiety disorders and other conditions, antidepressants target three essential neurotransmitters that are responsible for regulating your mood: dopamine, norepinephrine and serotonin.


This brain chemical plays an important role in the way you derive pleasure from behavioral and physical functions such as: learning, sleeping, paying attention to things around you, movement, staying motivated, and so much more.


Norepinephrine helps prepare your body and brain to spring into action, and increases your focus and alertness.


This neurotransmitter is responsible for regulating your social behavior, appetite, sleep, memory function, your mood, and sexual function.

Antidepressants are believed to affect how these neurotransmitters behave. Some of the most common antidepressants are known as reuptake inhibitors. A reuptake inhibitor prevents neurotransmitters from reabsorbing back into the nerve cells in the brain, after they have been released. This keeps the levels of these neurotransmitters high, improves communication between nerve cells, and strengthens mood regulation.

Different types of reuptake inhibitors target specific neurotransmitters. The three main types include selective serotonin reuptake inhibitors (SSRIs), serotonin and norepinephrine reuptake inhibitors (SNRIs) and norepinephrine and dopamine reuptake inhibitors (NDRIs). In this article, we will focus mainly on the difference between SSRIs and SNRIs.

What’s the Difference Between SSRIs and SNRIs?

What are SSRIs?

Selective serotonin reuptake inhibitors (SSRIs) are some of the most commonly prescribed types of antidepressants. Most of the antidepressants that are referenced in mainstream media and on the internet fall under this category, including Prozac, sertraline (Zoloft), citalopram (Celexa), escitalopram (Lexapro), fluvoxamine (Luvox) and paroxetine (Paxil), among several others.

These antidepressants help increase the level of serotonin in the brain by blocking the receptors that reabsorb it. In addition to treating depression, selective serotonin reuptake inhibitors (SSRIs) have been medically approved for the treatment of other conditions like anxiety, bulimia, fibromyalgia, hot flashes, obsessive-compulsive disorder (OCD), panic disorder, post-traumatic stress disorder (PTSD) and premenstrual dysphoric disorder.

What are SNRIs?

Serotonin and norepinephrine reuptake inhibitors (SNRIs) are a class of newer types of antidepressants. SNRIs are different from SSRIs as they prevent the reuptake of both serotonin and norepinephrine in the brain.

An imbalance of serotonin and norepinephrine is believed to be linked to the occurrence of anxiety disorders and panic disorder. These neurotransmitters regulate certain brain functions that can be affected at the onset of these conditions, including your mood, sleep, ability to focus, and stay alert. SNRIs can help in treating anxiety or panic disorders by keeping your serotonin and norepinephrine levels balanced.

Some of the best serotonin and norepinephrine reuptake inhibitors (SNRIs) that are approved for treatment include: desvenlafaxine (Pristiq), duloxetine (Cymbalta), levomilnacipran (Fetzima) and venlafaxine (Effexor XR) among others.

SNRIs aren’t only prescribed for the treatment of depression, anxiety disorders, and panic disorder, they’re also approved to treat bipolar disorder, chronic pain, social phobia, diabetic neuropathy, and osteoarthritis pain.

SSRI vs SNRI: Which is Better?

Selective serotonin reuptake inhibitors (SSRIs) and serotonin and norepinephrine reuptake inhibitors (SNRIs) are both approved for the treatment of a wide range of health conditions. Doctors often prescribe a combination of the two for their patients’ treatment, often in combination with norepinephrine and dopamine reuptake inhibitors (NDRIs).

In addition to their mood regulation function, SNRIs have the added effect of improving energy levels. But in practice, SSRIs tend to be more commonly prescribed for treating depression and other conditions than SNRIs because they are more effective at mood regulation and are less likely to cause side effects than some SNRIs.

It’s important to remember that both selective serotonin reuptake inhibitors (SSRIs) and serotonin and norepinephrine reuptake inhibitors (SNRIs) are different groups of prescription medication. Your provider is best equipped to adjust your dosage, switch or adjust the dosage of your medication when necessary, and give you advice on what might be the right fit for you.

What Are the Side Effects of SSRIs and SNRIs?

Selective serotonin reuptake inhibitors (SSRIs) and serotonin and norepinephrine reuptake inhibitors (SNRIs) have similar side effects, although they are more likely to occur with the use of some SNRIs.

The most commonly reported side effects of either SSRIs or SNRIs include blurred vision, constipation, dizziness, drowsiness, a dry mouth, gastrointestinal problems, headaches, insomnia, nausea, and reduced sexual desire.

Other reported side effects of both groups of medication include an increase in suicidal thoughts and feelings, especially in children and young adults below the age of 25 years. If you’re experiencing suicidal thoughts while taking an antidepressant, or you know someone who might be, call 911 or contact your doctor or an emergency resource immediately for help.

Serotonin syndrome may also occur where higher doses of SSRIs or SNRIs are administered, or when they interact with other medications that release serotonin, such as tramadol and dextromethorphan. Symptoms of serotonin syndrome include sweating, confusion, agitation, and a rapid heart rate.

Although SNRIs and SSRIs are relatively safe and not addictive, some of these medications have been linked with withdrawal-like symptoms when they are discontinued abruptly. These symptoms include dizziness, headache, muscle aches, tiredness, irritability, nausea, insomnia, and diarrhea. When it’s time to discontinue antidepressants, it helps to phase them out gradually. Consult your provider and therapist to come up with a plan for tapering from SSRIs or SNRIs.

Generally, the benefits of antidepressants for those suffering from depression are greater than the possible side effects. Finding the best medication for yourself depends on several factors, including the severity of your symptoms, and any other health conditions you may face concurrently.

What You Need to Know Before Taking Antidepressants

Whether a selective serotonin reuptake inhibitor (SSRI), a serotonin and norepinephrine reuptake inhibitor (SNRI) or a norepinephrine and dopamine reuptake inhibitor (NDRI) is prescribed for you, keep in mind that people react differently to the same medications. What works for you may not work so well for someone else, and vice versa. Additionally, it’s not uncommon to experience fewer or more side effects from a particular antidepressant than someone else.

Other factors can also affect the way you respond to medication, such as your symptoms, any health problems, other medications you’re taking at the time, and what has worked for you before. Your doctor or provider will make a note of these factors before issuing a prescription. It could also take a while before antidepressants become fully effective after you start taking them, so it helps to be patient and work closely with your doctor to figure out what works best for you.

Although conditions like depression, panic disorder, and anxiety disorders are associated with imbalances in neurotransmitters like serotonin, norepinephrine, and dopamine, SSRIs, SNRIs, or NDRIs can enhance the function of these neurotransmitters and offer relief to those suffering from these sometimes debilitating conditions. Therapy, however, can also help people work through depression in ways that prescription medication may be unable to and the treatments are frequently used in tandem. Therapy can also equip you with the necessary skills to cope and manage your depression.

While you work with your doctor to assess what kind of antidepressant will work best, online therapy is a good option to consider in order to get the help and support you need. If you’re looking for a provider to discuss medication, consider Talkspace online psychiatry services — the prescriptions you need, when you need them from a licensed prescriber — all from the comfort of your home.

Marris Adikwu

Marris is a freelance writer who is passionate about health and wellness, particularly in the areas of mental health and women’s health. She hopes that her articles will play a role in ensuring that these areas are discussed more widely. In her free time, she also writes short stories and reads anything she can get her hands on.

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