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Antidepressants: How they work and what they treat

Reviewed by Robert Bogenberger, PhD

An open yellow bottle lays on is side with white pills spilling out of it

Antidepressants are medications that can reduce symptoms of depression and other mental health conditions. All antidepressants are prescription medications, meaning a doctor or psychiatrist has to prescribe them for you.

Prior to the COVID-19 pandemic, 13.2% of adults in the US were using antidepressants.1 In February and March 2020, antidepressant prescriptions increased by 21%.2 Since then, antidepressant use has continued to increase around the world.

What antidepressants can treat

Antidepressants are commonly used to treat symptoms of moderate to severe depression, anxiety disorders, and other mood disorders.

Antidepressants may be prescribed for conditions including:

Doctors may also prescribe antidepressants for other conditions such as attention-deficit/hyperactivity disorder (ADHD) in children, eating disorders, and physical conditions that involve chronic pain.3, 4

How do antidepressants work?

Experts don’t completely understand how antidepressants work. For a long time, researchers thought they helped restore our brains’ balance of neurotransmitters, chemicals involved with our moods, emotions, and other processes.5 Today, a preferred theory is that part of what antidepressants do is help the brain grow new connections between cells.6  

Types of antidepressants

Antidepressants may be prescribed by physicians, nurse practitioners, physician assistants, and, in some states, psychologists. Your provider will help you decide what type of antidepressant medication may help based on your symptoms, your medical history, medication side effects, and other factors such as drug interactions.

Major classes of antidepressant include the following:

  • Selective serotonin reuptake inhibitors (SSRIs), the most commonly prescribed type of antidepressant, are generally prescribed for depression, anxiety, panic disorders, and OCD. Examples include fluoxetine (Prozac), sertraline (Zoloft), and escitalopram (Lexapro).
  • Serotonin-norepinephrine reuptake inhibitors (SNRIs) are usually prescribed to treat depression, some anxiety disorders, and chronic pain. Examples include duloxetine (Cymbalta), venlafaxine (Effexor), and desvenlafaxine (Pristiq).
  • Tricyclic antidepressants (TCAs), an older class of antidepressant, may be prescribed if SSRIs or other medications don’t lessen symptoms of depression or chronic pain. Examples include amitriptyline (Elavil) and nortriptyline (Pamelor or Aventyl).
  • Monoamine oxidase inhibitors (MAOIs) aren’t as commonly prescribed these days because they’re known to interact with certain foods, drinks, and medications.7 However, they may be prescribed for depression and other mental health conditions when other antidepressants don’t work. Examples include phenelzine (Nardil) and tranylcypromine (Parnate).
  • Atypical antidepressants don’t fall under any of the classes listed above. Again, they’re often prescribed when other antidepressants aren’t effective or cause intolerable side effects. Examples include vortioxetine (Trintellix) and vilazodone (Viibryd).

Benefits of taking antidepressants

Antidepressants can lessen symptoms of depression, anxiety, and other mental health issues. They may:8

  • Help you feel calmer and more in control of your thoughts, feelings, and behaviors.
  • Reduce feelings of sadness, hopelessness, and worthlessness.
  • Reduce worry, unease, and restlessness.
  • Improve mood and increase energy levels.
  • Improve concentration, decision-making, and communication skills.
  • Boost motivation, productivity, and engagement with activities.
  • Improve the way your body perceives and processes pain signals.9
  • Reduce fatigue associated with chronic pain, regulate sleep, and reduce pain levels.10

Note that antidepressants may lessen your symptoms and help you manage them, but they won’t necessarily get rid of them entirely.

Antidepressant side effects

Many people who take antidepressants experience side effects, though how serious they are and what side effects a person has can vary. Commonly reported ones include:

  • Anxiety
  • Agitation
  • Dry mouth
  • Blurred vision
  • Headache
  • Dizziness
  • Appetite changes
  • Weight gain
  • Digestive issues
  • Decreased libido
  • Insomnia

If you experience concerning or serious side effects while taking antidepressants—especially if you feel worse or have thoughts of suicide—contact your doctor or mental health care provider right away. They may want to adjust your dosage or switch you to a different type of antidepressant.

If you’re in crisis, please call or text the 988 Crisis Lifeline at 988 for free, confidential support 24 hours a day, 7 days a week.

How effective are antidepressants?

Hundreds of clinical trials have shown that antidepressants are effective at helping people manage their mental health symptoms.11 However, it’s not easy to predict how effective a particular antidepressant will be for a given person. Everyone’s situation is unique, and a certain antidepressant drug that works for others may or may not work for you.

Studies suggest that the more severe your depression, the more effective antidepressants tend to be.12 People with mild depression may see minimal or no effects.

Clinicians often start by prescribing an antidepressant they believe will be both effective and tolerable. If your symptoms don’t improve, you may be prescribed a different medication. It can sometimes take trying several antidepressants before you start feeling better.

Long-term use, health risks, and discontinuation

Clinicians usually recommend taking antidepressants for at least six to nine months before stopping them, to lessen the risk of relapse.13

Research shows that more Americans are taking antidepressants for long periods of time. In a nationally representative study, nearly 25% of people had been on them for 10 years or more as of 2014.14 One UK study showed that more than half of participants who were on antidepressants relapsed after they discontinued them, suggesting that some people may be better off taking them long-term.15

This is significant given the possibility of health risks. One 2017 study suggested antidepressant users have a 14% higher risk of stroke or heart attack compared to those who don’t use them.16 Another study suggested older adults on antidepressants may have an increased fall risk.17  On the other side of the coin, untreated depression carries its own potential health hazards, including substance abuse and suicide.18

If you decide to stop taking an antidepressant, note that you’ll need to gradually lower (or “taper”) the dose over time under a doctor’s supervision. This will help you avoid unpleasant side effects of sudden discontinuation, such as nightmares, disturbing thoughts, and various physical symptoms.

Why an antidepressant may lose effectiveness

Sometimes, an antidepressant will become less effective over time.19 This is called antidepressant tolerance or “breakthrough” depression, which can happen when the body grows accustomed to the effects of the antidepressant and stops responding to it as strongly.

Other factors known to interfere with antidepressants’ effectiveness include:20

Why antidepressants don’t always work

Depression is a complicated condition, with causes that can vary from person to person. Underlying factors may include:21

  • Genetic factors, such as a family history of depression
  • Brain chemistry interactions
  • Environmental factors such as childhood trauma or chronic stress

Around 10 to 30% of people with major depression have symptoms that don’t respond to antidepressant treatment—this is called treatment-resistant depression.22 Those patients may require additional medications, psychotherapy, or alternative treatments.

How do you know if you need antidepressants?

Your doctor or mental health care provider can help you decide whether antidepressants are a good choice for you. They should consider your symptoms, review your physical and mental health history, and go over a medication’s benefits and risks with you. They may recommend additional lifestyle changes, psychotherapy, or other treatments alongside (or as alternatives to) antidepressants.

If your provider recommends medication, ask questions about its potential side effects and interactions with other medications you may be taking. If you’re interested in alternative or complementary treatment options, get your doctor’s take on whether they’re likely to be safe and effective.

Visit our directory to find a licensed therapist who can help you make informed decisions about your mental health.

About the author

The editorial team at works with the world’s leading clinical experts to bring you accessible, insightful information about mental health topics and trends.