Selective serotonin reuptake inhibitors (SSRIs) and serotonin-norepinephrine reuptake inhibitors (SNRIs) are two different types of antidepressants.
Both SSRIs and SNRIs act on neurotransmitters, which are chemicals in the brain that help carry nerve signals between neurons. SSRIs increase serotonin levels in the brain, while SNRIs increase serotonin and norepinephrine levels.
Keep reading to learn more about the differences between these two types of medications, including how they work, the conditions that doctors may use them to treat, and the associated side effects.
Cells in the brain make neurotransmitters, including serotonin and norepinephrine, which some people may call noradrenaline. Neurons, which are cells in the brain, are
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.
SNRIs and SSRIs
The reuptake process reduces the availability of neurotransmitters because the brain reabsorbs them. Therefore, by blocking this process, reuptake inhibitors increase the availability of neurotransmitters.
Serotonin helps the body regulate mood. When serotonin is too high or too low, a person may become depressed. Low serotonin can also cause anxiety, suicidal thoughts, depression, or obsessive-compulsive behaviors. When serotonin levels rise, a person may feel less physically and psychologically active or aroused, making it easier to sleep and relax.
SSRIs and SNRIs both increase serotonin levels in the brain, potentially helping with the symptoms of various mental health conditions.
Norepinephrine plays a key role in the fight-or-flight reaction. During times of intense stress, such as when a person feels threatened, norepinephrine naturally increases.
In daily life, norepinephrine also plays a role in sleep, attention, memory, and mood regulation. People with low levels of norepinephrine may have trouble concentrating, develop symptoms of attention deficit hyperactivity disorder (ADHD), or show signs of depression.
SNRIs increase norepinephrine levels, helping a person concentrate and reducing depression.
Higher levels of norepinephrine may cause feelings of euphoria. However, they may also cause panic attacks, high blood pressure, and hyperactive behavior. Due to these effects, SNRIs may not be suitable for people with certain heart health issues, a history of panic, or problems with hyperactivity.
There is no conclusive evidence that either group of drugs is consistently superior to the other for all individuals. A person may need to experiment with different drugs or combinations of drugs at different dosages.
Both classes of drugs can take several weeks to work.
Both SNRIs and SSRIs play a wide variety of roles in a person’s health and daily functioning. For example, serotonin helps regulate a person’s waking and sleeping rhythms, appetite, digestion, and endocrine system.
These diverse functions mean that SSRIs and SNRIs can cause a wide range of side effects.
The specific side effects that people experience vary among individuals, and they may also change over time or with higher dosages. Some people find certain side effects more troubling than others, so it is important to make a doctor aware of any specific concerns.
In some cases, a person may experience no side effects, or the side effects may go away as their body adjusts to the drug.
Some of the
- sexual dysfunction, including trouble becoming aroused, changes in libido, and difficulty reaching orgasm
- gastrointestinal upset
- changes in sleep
- agitation
- fatigue
- dry mouth
Although less common, some more serious side effects can also occur. These include:
- suicidal thoughts or worsening depression, particularly among children and teenagers
- allergic reactions
- eye pain and changes in sight
- rash
- manic episodes
- seizures
- changes in weight or appetite
- an irregular heart rate
- serotonin syndrome, which is a potentially life threatening condition
SNRIs can cause similar side effects as SSRIs. Other possible side effects of these antidepressants may include:
- constipation
- nausea
- loss of appetite
- dizziness
- headaches
Some people may also experience symptoms of withdrawal after they stop taking either class of drugs.
Some of the conditions that SSRIs and
- forms of depression, such as major depressive disorder, seasonal affective disorder, and the depressive episodes of bipolar disorder
- anxiety disorders, such as generalized anxiety disorder, phobias, and obsessive-compulsive disorder (OCD)
- post-traumatic stress disorder (PTSD)
- suicidal thoughts
- fibromyalgia and other types of chronic pain
Some SNRIs can treat diabetic neuropathy. Doctors may also use these drugs on an off-label basis to treat other conditions, such as sleep disorders.
While many drugs sit within one of these two categories, each specific drug behaves a little differently in the body. A person who does not like the side effects of one member of a drug group might still do well on a different drug that belongs to the same category.
Some SSRIs include:
- fluoxetine
- citalopram
- sertraline
- paroxetine
- escitalopram
- fluvoxamine
- vilazodone
Some examples of SNRIs include:
- venlafaxine
- duloxetine
- desvenlafaxine
- milnacipran
- levomilnacipran
Some commonly asked questions about SSRIs and SNRIs may include:
Are SNRIs better than SSRIs?
Both SNRIs and SSRIs are effective antidepressants for treating conditions such as depression. Generally, SNRIs may be more effective than SSRIs, but they are also more likely to cause side effects.
How do you know if you should take an SSRI or SNRI?
A doctor will prescribe the most suitable medication depending on a person’s symptoms and medical history. For example, with depression, SSRIs are usually the first line of treatment as they offer a greater benefit-to-risk ratio.
Do SNRIs give you energy?
SNRIs work by boosting serotonin and norepinephrine. Both of these neurotransmitters can influence energy levels, so a person may notice that they feel more energetic.
Are SNRIs harder to get off than SSRIs?
When stopping antidepressants such as SNRIs or SSRIs, it is advisable to slowly taper off the drug under medical guidance. Generally, SNRIs are more likely to cause discontinuation symptoms.
However, multiple factors, such as the individual, antidepressant, duration, and dosage, can influence the likelihood of potential discontinuation symptoms.
Both SSRIs and SNRIs can help treat a range of mood issues, as well as some other conditions, such as chronic pain. When a person takes these drugs under the supervision of a doctor, they can dramatically improve the quality of life.
However, too much of any neurotransmitter can negatively affect health and well-being. Therefore, people seeking mental health treatment should share with their doctor all of their symptoms, their complete medical history, and a list of all the drugs that they are taking, including supplements and over-the-counter medications.
It may take time and a little experimentation to find a medication that works, so people should try to work with a doctor who is willing to explore all options and listen carefully to concerns about side effects.