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SNRIs vs SSRIs: What are their differences, similarities, and how do they work?

SNRIs vs SSRIs: What are their differences, similarities, and how do they work?

Antidepressants are a widely prescribed class of medication that works to treat the symptoms of anxiety, depression, and other conditions. Two types of antidepressants, selective serotonin reuptake inhibitors (SSRIs) and serotonin-norepinephrine reuptake inhibitors (SNRIs), are some of the most popular.

SSRIs and SNRIs both work by increasing the amounts of certain brain chemicals that affect our mood and stress levels. But many who learn about these two medications may want to compare SNRIs vs SSRIs. 

Learn more about how these drugs are similar, how they’re different, how they work, and what disadvantages there may be to taking one or the other. Then consider whether a provider could help you determine whether SSRIs or SNRIs are right for you. 

SSRIs vs SNRIs: What’s the Difference?

SSRIs and SNRIs are both antidepressant drugs. Both medications are typically prescribed to treat:

There’s more to their differences than just their names, though. While SSRIs affect only serotonin levels in the body (as their name implies), SNRIs affect both serotonin and norepinephrine. SSRIs block serotonin reuptake, while SNRIs stop the reuptake of both serotonin and norepinephrine

You may be wondering what “reuptake” actually means. When chemicals like serotonin and norepinephrine are produced and released through the brain, they are gradually reabsorbed through what is known as the reuptake process. This process reduces the availability of neurotransmitters, brain structures that aid in chemical signaling and other complex functions. 

SSRIs and SNRIs affect this process. Without an SSRI or SNRI, the brain’s reuptake process naturally reduces the availability of neurotransmitters, many of which interact with serotonin and norepinephrine. Some of these are known excitatory neurotransmitters

They promote electrical signals in the brain, and in short, these signals have a stimulating effect. But inhibitory neurotransmitters tend to weaken or slow nerve signals—leading to a calming effect.

Serotonin has a bit more complex function in the brain, at least concerning mood regulation, than norepinephrine. It can create both stimulating and calming effects, while norepinephrine (which is also known as adrenaline) is entirely stimulating.

When someone is suffering from depression or anxiety, their body’s serotonin or norepinephrine levels could be too high or too low, and their mood can be affected as a result. By taking an SSRI or SNRI to help balance out their brain chemistry, individuals can improve their ability to cope with anxiety symptoms, and may be able to better cope with difficult situations, stressful emotions, and more. 

SSRIs vs SNRIs: Which Is Better?

It’s interesting to compare SSRIs vs SNRIs, but neither drug is superior to the other. Both SSRIs and SNRIs are both popular options for treating anxiety and depression in different ways. 

In the SSRIs vs SNRIs debate, it’s important to remember that these medications work to achieve the same goal: To alleviate depression and anxiety symptoms (among other conditions) by helping the brain to better regulate serotonin and/or norepinephrine levels. 

What Are the Differences and Similarities Between SSRIs and SNRIs?

When we compare SNRIs vs SSRIs, they both prevent the reuptake of certain neurotransmitters in the brain. SSRIs block serotonin reuptake, while SNRIs stop the reuptake of both serotonin and norepinephrine

Different neurotransmitters carry different types of signals. Some, called excitatory neurotransmitters, increase the chance of the neuron generating an electrical signal called an action potential. Inhibitory neurotransmitters, by contrast, weaken or slow nerve signals. 

Serotonin can serve both excitatory and inhibitory roles, while norepinephrine is a purely excitatory neurotransmitter.

The reuptake process reduces the availability of neurotransmitters because the brain reabsorbs them. By blocking this process, SSRIs and SNRIs increase the availability of serotonin and/or norepinephrine.

When your body’s serotonin or norepinephrine levels are either too high or too low, your mood can be affected. This can make you feel more anxious or worried and may even lead to more severe anxiety disorders or types of depression. 

Taking an SSRI or SNRI helps balance these brain chemicals, significantly reducing anxiety symptoms to help you face stressful situations better.

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Are SNRIs Better than SSRIs for Anxiety?

Neither prescription is necessarily better than the other; but SSRIs may be more effective than SNRIs in certain situations, and vice versa. Compare the two types of medications below: 

SSRIs tend to

  • Be more widely used than SNRIs 
  • Be considered before SNRIs as the first line of defense against anxiety and depression, at least according to one review
  • Have less severe side effects compared to SNRIs 

In comparison, SNRIs

  • Might be more effective in treating severe depression symptoms
  • May be better for improving energy and concentration
  • Could be better at treating panic disorder

But in general, comparing these medications in reviews and studies has typically concluded that there are little to no major differences in their overall effectiveness or safety. Their differences tend to be modest. Talking with your psychiatric provider can help you determine between SSRIs vs SNRIs which antidepressant is best for you.

Why Use an SNRI for Anxiety Disorders When Norepinephrine Is a Stimulant?

Anxiety and norepinephrine might seem closely related, right? They are—kind of. Norepinephrine activates the amygdala, a deep, primal part of the brain known for producing fear-related behavior. SNRIs can help reduce activity in this area of the brain, positively affecting a person’s mood, reduce feelings of anxiety, and help alleviate panic attacks.

This is because it’s not always about removing norepinephrine, but helping the brain regulate the amounts of this neurotransmitter. It’s true that during times of intense stress, such as when a person feels threatened, norepinephrine naturally increases. 

But even though norepinephrine plays a key role in our fight-or-flight reactions, over time, chronic stress and anxiety can lead to a shortage of this neurotransmitter, and this can actually make someone’s anxiety worseNorepinephrine also affects our sleep patterns, ability to pay attention, working and long-term memory, and mood. When someone with low levels of norepinephrine doesn’t receive the treatment they need, they might show symptoms of ADHD, anxiety, or warning signs of depression.

Do SNRIs Work Faster than SSRIs?

SNRIs may achieve slightly faster antidepressant effects than SSRIs by elevating the concentrations of dopamine in the brain. SNRIs may take 2-4 weeks to kick in completely, while SSRIs may take 2-8 weeks. 

The speed at which a medication kicks in depends on the dosage, as well as the patient’s physical status, the time of day the prescription is taken, and a range of other factors.

What Is a Disadvantage of SSRIs and SNRIs?

When it comes to SSRIs vs SNRIs, these antidepressants have the ability to reduce your sex drive or sexual functioning in some instances—and these medications may be more likely than others to cause sexual side effects. Around 1 in 5 adults in the US experiences sexual side effects due to antidepressants, most commonly in SSRIs. 

These symptoms are usually mild, but may include delayed lubrication, delayed or blocked orgasm, or trouble maintaining an erection. Sleeping issues are a common complaint of people with depression—and people who are taking an SNRI or SSRI for a depressive disorder may experience difficulty sleeping. 

However, it’s not always clear whether one’s sleeping issues are being caused by the medication or their depression. But over time, antidepressants typically help improve sleeping issues and sleep quality. 

SSRIs and SNRIs  list weight gain as a side effect Not everyone will experience this. But as someone’s mood improves, they may start to experience an increased appetite, which can cause weight gain. 

Do SSRIs and SNRIs Have Other Side Effects?

When it comes to SSRIs vs SNRIs, they have many overlapping side effects. Some possible SSRI side effects include:

  • Anxiety
  • Sinus inflammation or infections
  • Rashes
  • Sweating
  • Fatigue

In rare cases, SSRIs may also contribute to: 

  • Vision problems
  • Allergic reactions
  • Suicidal thoughts
  • Serotonin syndrome
  • Irregular heart beat

Some of the most commonly reported side effects of SNRIs include:

  • Sweating
  • Fatigue
  • Nausea
  • Dry mouth
  • Dizziness
  • Sweating
  • Headache 
  • Anxiety
  • Sinus infections
  • Rashes

SNRIs may rarely cause: 

  • Constipation
  • Sexual dysfunction
  • Changes in appetite
  • Increased blood pressure
  • Liver problems
  • Serotonin syndrome 

Side effects are typically rare—and a psychiatric provider will discuss the possible risks, benefits, and long-term outcome of SSRIs vs SNRIs. 

SNRIs vs SSRIs: Which Is Right For You?

If you think that you’re struggling with depression or anxiety, or another condition that seems treatable with an antidepressant, it could be a good idea to talk with a provider or your doctor. 

They can help you decide between an SSRI vs SNRI, and offer supplementary coping strategies and self-care techniques that work together with your prescription. And with the right prescription, dosage, and treatment plan, you won’t be stuck comparing SSRIs vs SNRIs, as either medication could drastically improve your quality of life.

  • Medical reviewer
  • Writer
  • 5 sources
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George Ramos, PMHNP-BCBoard-Certified Psychiatric Mental Health Nurse Practitioner
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George Ramos is a board-certified Psychiatric Mental Health Nurse Practitioner (PMHNP-BC). He specializes in coping skills, anxiety, depression, ADHD, and bipolar disorder.

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Jason CrosbyMental Health Writer

Jason Crosby is a Senior Copywriter at Thriveworks. He received his BA in English Writing from Montana State University with a minor in English Literature. Previously, Jason was a freelance writer for publications based in Seattle, WA, and Austin, TX.

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