What Are Antidepressants?

Antidepressants are prescription medications typically used to treat depression and other mental health conditions. 

Clinical depression, also called major depressive disorder (MDD), involves ongoing feelings of sadness, emptiness, apathy, and worthlessness. It can also cause symptoms like fatigue, problems with sleep, appetite changes, irritability, and chronic pain. 

Antidepressants help reduce these symptoms by balancing the level of certain neurotransmitters (chemical messengers) in the brain. Estimates suggest that about 13% of U.S. adults take antidepressants. Women are over twice as likely as men to take antidepressants regularly.

This article discusses antidepressants, including types, side effects, uses, effectiveness, and more.

Healthcare provider discussing antidepressant with person seeking care

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Types of Antidepressants

There are several different types of antidepressants. Each one acts on the brain differently to reduce the symptoms of depression. Learn more about the most common types of antidepressants and how they work.

Serotonin and Noradrenaline Reuptake Inhibitors (SNRIs)

Serotonin and noradrenaline reuptake inhibitors (SNRIs) are popular antidepressants that increase the level of two different neurotransmitters—serotonin and noradrenaline—in the brain. 

Serotonin is involved with mood, memory, learning, and emotion. Noradrenaline, also called norepinephrine, helps you manage stress and remain calm during a crisis.

SNRIs work by inhibiting the reuptake of serotonin and noradrenaline by the neurons that release them. They stop these neurotransmitters from being reabsorbed. This increases the amount of serotonin and noradrenaline available in your brain. 

Some common SNRIs include:

  • Effexor XR (venlafaxine)
  • Cymbalta (duloxetine)
  • Pristiq (desvenlafaxine)
  • Fetzima (levomilnacipran)

Selective Serotonin Reuptake Inhibitors (SSRIs)

Selective serotonin reuptake inhibitors (SSRIs) are the most common type of antidepressants.  SSRIs work by blocking the reuptake of serotonin in the brain. This can help improve mood and motivation, relieving depression symptoms and bringing about a greater sense of stability and well-being. 

Popular SSRIs include:

Tricyclic Antidepressants (TCAs)

Tricyclic antidepressants (TCAs) belong to an older class of medications known as first-generation antidepressants. Like SNRIs, TCAs work to block the reuptake of serotonin and noradrenaline. They also affect the activity of acetylcholine—a neurotransmitter involved in memory and learning.

Due to their side effects, TCAs were largely replaced by SSRIs in the U.S. in 1988. Although newer antidepressants are typically the first-choice treatment for depression, the benefits of traditional antidepressants like TCAs may still outweigh the risks for some people. 

Some common TCAs include:

  • Elavil (amitriptyline)
  • Anafranil (clomipramine)
  • Pamelor (nortriptyline)
  • Norpramin (desipramine)
  • Tofranil (imipramine)

Monoamine Oxidase Inhibitors (MAOIs)

Like TCAs, monoamine oxidase inhibitors (MAOIs) are first-generation antidepressants that are no longer widely used due to side effects. 

MAOIs work to treat depression by reducing, or “inhibiting,” the activity of two enzymes: monoamine oxidase A (MAO-A) and/or monoamine oxidase B (MAO-B). This helps to balance levels of neurotransmitters like serotonin, noradrenaline, and dopamine in order to increase motivation and regulate mood.

Examples of MAOIs include:

  • Parnate (tranylcypromine)
  • Nardil (phenelzine)
  • Marplan (isocarboxazid)

Noradrenergic and Specific Serotoninergic Antidepressants (NaSSAs)

Noradrenergic and specific serotoninergic antidepressants (NaSSAs) are sometimes used to treat depression if more common antidepressants aren’t effective. 

Sometimes called “atypical antidepressants,” NaSSAs work similarly to tetracyclic antidepressants (TeCAs), which are related to TCAs. In the U.S., the most common NaSSA is Remeron (mirtazapine).

Side Effects

While antidepressants are generally considered safe to use, many people experience some side effects while taking them. Some of the most common side effects of antidepressants include:

  • Drowsiness and fatigue
  • Unwanted weight gain and appetite changes
  • Sexual changes, such as loss of libido (desire to have sex) or difficulty reaching orgasm
  • Nausea, vomiting, and indigestion
  • Constipation
  • Insomnia
  • Headaches
  • Dry mouth
  • Mood changes, such as irritability and anxiety
  • Shaking
  • Dizziness
  • Water retention/bloating
  • Excessive sweating

For many people, the side effects of antidepressants go away on their own with time. Others find that the benefits of antidepressants outweigh the side effects. 

However, some people who take antidepressants experience more persistent or severe adverse effects. For SSRIs and SNRIs, these may include:

  • Post-SSRI sexual dysfunction (PSSD): Many people who take SSRIs and SNRIs experience some sexual side effects. Possible side effects include erectile dysfunction, reduced sex drive, difficulty achieving orgasm, genital numbness, premature ejaculation, loss of pleasure during sex, and abnormal orgasm. For some people, these side effects are long-lasting, even persisting months or years after they stop taking antidepressants.
  • Serotonin syndrome (SS): Serotonin syndrome is a potentially fatal condition caused by an excessive amount of serotonin in the body. Symptoms may include restlessness, agitation, confusion, problems with coordination, rapid heart rate, and tremors. Many antidepressants can cause serotonin syndrome, but researchers believe that people taking SSRIs and MAOIs have the highest risk. 
  • Hypertension (high blood pressure): Studies indicate that people who take SNRIs have an increased likelihood of developing high blood pressure.
  • Hyponatremia (low blood sodium): Hyponatremia is a dangerous drop in blood sodium levels that can lead to symptoms like muscle weakness, confusion, and convulsions. Older people who take SSRIs are especially at risk for hyponatremia.
  • Gastrointestinal bleeding: Some research suggests that SSRIs and certain SNRIs increase the risk of problems with bleeding, especially abdominal bleeding.

Older antidepressants, such as TCAs and MAOIs, have been linked to a number of serious side effects. These include: 

  • Heart problems, such as arrhythmia (irregular heartbeat) and hypertension
  • Liver damage
  • Vision problems
  • Seizures

Meanwhile, severe side effects of NaSSAs may include:

  • Psychosis (a break from reality), including delusions (persistent false beliefs) and hallucinations (seeing or hearing things that aren’t there)
  • Tachycardia (increased heart rate)
  • Hypertension 

If you experience any unwanted side effects from antidepressants, talk to your healthcare provider. You may be able to change your dose or switch to a different medication. 

In rare cases, antidepressants can increase the risk of suicidal thoughts, especially among people under 25. If you are having thoughts of self-harm or suicide, seek emergency medical help.

Seek Help

If you are experiencing thoughts of self-harm or suicide, call the National Suicide Prevention Lifeline at 800-273-8255, talk to your healthcare provider, or talk to a mental health professional. If you or someone else is at immediate risk, dial 911.

Uses

Antidepressants are primarily used to treat depression. In some cases, they may be prescribed to manage the symptoms of other mental health conditions, such as: 

Due to their role in managing chemical imbalances within the brain, antidepressants are also sometimes used to treat physical and neurological conditions. Healthcare providers sometimes prescribe antidepressants to treat the following medical conditions:

  • Chronic pain conditions: Some antidepressants are effective in treating conditions that involve long-term pain, such as fibromyalgia. Cymbalta is approved for the treatment of fibromyalgia by the Food and Drug Administration (FDA). Research suggests that Elavil is also highly effective in managing fibromyalgia symptoms.
  • Insomnia: Antidepressants may be prescribed for off-label use in treating insomnia. One review found that both TCAs and SSRIs were effective in improving sleep quality and increasing sleep time.
  • Migraine: There is a growing body of evidence that certain TCAs and SNRIs can be used to prevent migraine headache in adults.
  • Multiple sclerosis (MS): Multiple sclerosis is an autoimmune disorder that causes damage to the nervous system, resulting in symptoms like prickling sensations, muscle weakness, and blurred vision, as well as problems with balance, coordination, thinking, and memory. Studies suggest that certain antidepressants can help manage MS symptoms and prevent flare-ups.

Effectiveness

Antidepressants are usually effective in treating moderate to severe depression. 

Estimates suggest that antidepressants typically reduce depressive symptoms by about 67%. In one study, over 89% of people who were taking antidepressants on a long-term basis reported that their medication had improved their symptoms. 

While all FDA-approved antidepressants have been shown to alleviate symptoms of depression, estimates of the effectiveness of each type vary widely. One systematic review and meta-analysis found that Effexor XR, Paxil, Remeron, and Elavil were more effective than Prozac and Luvox on average.

However, many people stop taking antidepressants due to negative side effects (about 44% of people stop taking their medication within just three months). This may lead to relapse or withdrawal symptoms. Around 56% of people who stop taking an antidepressant experience at least some withdrawal symptoms for several weeks or months. 

If you plan to stop taking antidepressants, you should only do so with the help and guidance of your healthcare provider. They can help you reduce your dose gradually and safely.

Antidepressants in Pregnancy

Some people worry about the safety of taking antidepressants during pregnancy. According to the Centers for Disease Control and Prevention (CDC), taking certain SSRIs—especially Prozac or Paxil—early in pregnancy may increase the risk of birth defects. These may include:

  • Heart defects
  • Anencephaly, which affects the baby’s skull and brain
  • Abdominal defects

Meanwhile, up to 30% of babies exposed to SSRIs during the later stages of pregnancy will develop neonatal adaptation syndrome after birth. Babies with neonatal adaptation syndrome experience symptoms like difficulty breathing, problems with feeding, jitteriness, and irritability.

However, untreated depression can also increase the risks of health complications for both you and your baby. Discuss your options with your healthcare provider if you take antidepressants and are pregnant or trying to become pregnant. They can help you decide whether a lower dose or a different medication may be right for you.

Alternatives

While they are effective for many people, antidepressants aren’t the only way to alleviate symptoms of depression. Here are some other ways you may be able to find relief:

  • Psychotherapy: Psychotherapy (talk therapy), such as cognitive behavioral therapy (CBT), is typically the first-choice treatment for depression. Talk therapy may be used on its own or alongside antidepressants.
  • Other medications: If antidepressants don’t improve your symptoms, your healthcare provider may suggest another medication, such as a mood stabilizer.
  • Support groups: Self-help and peer support groups, whether online or in-person, can help you find a supportive community and valuable resources.
  • Exercise: Getting enough exercise regularly can significantly reduce the harmful effects of depression—both physical and psychological.
  • Mindfulness: Practicing mindfulness techniques, such as meditation and yoga, can help boost your mood and improve your sense of well-being.
  • Herbal remedies: While evidence about their effectiveness is limited, some studies suggest that herbs like saffron and lavender may work to reduce mild anxiety and depression symptoms.

Summary

Antidepressants are medicines that are prescribed to treat clinical depression. They may also be used to treat other mental health conditions, as well as insomnia and chronic pain.

The main types of antidepressants are selective serotonin reuptake inhibitors, serotonin and noradrenaline reuptake inhibitors, tricyclic antidepressants, monoamine oxidase inhibitors, and noradrenergic and specific serotoninergic antidepressants.

Antidepressants typically work to regulate mood by increasing the level of certain neurotransmitters—such as serotonin, noradrenaline, and dopamine—in the brain. 

Some of the most common side effects of antidepressants include fatigue, sexual side effects, weight gain, dry mouth, dizziness, constipation, and indigestion. Severe side effects from antidepressants, such as abnormal bleeding, heart problems, and high blood pressure, are rare.

A Word From Verywell

If you’re experiencing symptoms of depression, reach out to your healthcare provider. Antidepressants may help boost your mood, reduce fatigue, and improve your overall outlook on life. Your healthcare provider can also suggest other ways to address depression, either alongside medication or as an alternative.

Frequently Asked Questions

  • How long does it take for antidepressants to work?

    It typically takes antidepressants about four to eight weeks to work. Some people may see improvements earlier. After they start to experience the benefits of antidepressants, most people take them for about six to 12 months under the advice of their healthcare provider.

  • Why do antidepressants cause weight gain?

    Researchers haven’t identified a single clear reason as to why antidepressants cause weight gain. Certain antidepressants may affect the body’s metabolism rate. Meanwhile, some antidepressants may increase appetite and cause intense food cravings. Common side effects like fatigue and drowsiness may cause some people to reduce their physical activity.

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