Antidepressants

Reviewed by Michael Callans, Master’s in Psychology · Last updated June 2026

What are antidepressants?

Antidepressants are prescription medications used to treat depression and a range of other conditions, including anxiety, OCD, panic disorder, and PTSD. They work on chemical messengers in the brain that influence mood, sleep, appetite, and concentration.

They are among the most widely prescribed and most studied medicines in mental health. As the National Institute of Mental Health (NIMH) explains, antidepressants such as SSRIs and SNRIs are commonly prescribed because they improve symptoms across a broad group of depressive and anxiety disorders. That breadth is one reason you may be offered an antidepressant for a condition other than depression.

Antidepressants are not sedatives or stimulants, and they are not addictive in the way some other drugs are. They are often used alongside psychotherapy, and for many people the combination of medication and therapy works better than either approach alone. They are not a quick fix and not a personality change in a pill; the goal is to ease symptoms enough that recovery, therapy, and daily life become more workable.

It is also worth knowing that antidepressants are prescribed for more than depression. The same medicines are used for several anxiety disorders, OCD, panic disorder, PTSD, and sometimes for chronic pain or sleep, depending on the medication. So being offered an antidepressant does not necessarily mean a clinician thinks you have depression. If you are unsure why a particular medicine was suggested, it is reasonable to ask your prescriber what they are aiming to treat and what success would look like.

Main types of antidepressants

There are several classes of antidepressants. They differ in which brain chemicals they act on and in their side-effect profiles, which is why a prescriber chooses among them based on your symptoms, other health conditions, and how you respond. The MedlinePlus resource from the US National Library of Medicine groups them into newer antidepressants, usually tried first, and older ones often reserved for when the newer options do not work.

• SSRIs (selective serotonin reuptake inhibitors): usually the first choice because they are effective and generally well tolerated. They mainly increase the availability of serotonin in the brain. Examples include fluoxetine, sertraline, escitalopram, citalopram, and paroxetine.
• SNRIs (serotonin and norepinephrine reuptake inhibitors): act on two brain chemicals, serotonin and norepinephrine. They are a common alternative when an SSRI has not helped enough, and some are also used for chronic pain. Examples include venlafaxine, desvenlafaxine, and duloxetine.
• Atypical antidepressants: a varied group that does not fit neatly into the other classes and works in different ways. Examples include bupropion, which is less likely to cause sexual side effects and is sometimes used to help with smoking cessation, and mirtazapine, which can aid sleep and appetite.
• Tricyclic antidepressants (TCAs): older medications such as amitriptyline and nortriptyline. They are effective but tend to cause more side effects and can be dangerous in overdose, so they are used less often as a first option and are sometimes prescribed for pain or sleep.
• MAOIs (monoamine oxidase inhibitors): among the oldest antidepressants, such as phenelzine and tranylcypromine. They are very effective but require dietary restrictions (avoiding aged and fermented foods high in tyramine) and careful attention to drug interactions, so they are usually reserved for cases that have not responded to other options.

How they work

Antidepressants adjust the activity of neurotransmitters such as serotonin, norepinephrine, and dopamine, which help regulate mood, sleep, and emotion. As MedlinePlus puts it, researchers think antidepressants may help improve the way the brain uses certain chemicals that control mood or stress. Different classes act on different chemicals and through different mechanisms, which is part of why one medication can suit a person better than another.

The exact way antidepressants improve symptoms is still being studied. They appear to support gradual changes in brain function rather than producing an instant lift, so the goal is steady, lasting improvement over weeks, not an immediate change in how you feel.

What to expect

Most people do not feel better right away. According to the NIMH, antidepressants take time, usually four to eight weeks, to work, and problems with sleep, appetite, energy, and concentration often improve before mood lifts. The UK's National Health Service (NHS) similarly notes that antidepressants usually take one to two weeks to start having an effect and can take up to eight weeks to work fully. That early window, before the benefits arrive, is when support and patience matter most.

Finding the right fit may involve trying more than one medication or adjusting the dose. This is normal and does not mean treatment will not work for you. People differ in how they respond to each medicine, partly because of differences in body chemistry, so the first prescription is a starting point rather than a final answer. Keep taking the medication as prescribed even once you feel better, and review progress with your prescriber rather than judging the medicine in the first few days. Keeping a simple note of your sleep, energy, and mood between appointments can help you and your prescriber see whether it is working.

Common side effects

Side effects vary by medication and person. The NIMH notes that common side effects of SSRIs and other antidepressants, such as upset stomach, headache, or sexual difficulties, are generally mild and tend to go away with time. Common ones include:

• Nausea or upset stomach
• Headache
• Changes in sleep or appetite
• Dry mouth
• Sexual side effects
• Feeling restless or drowsy

Tell your prescriber about any side effects, especially if they are severe or do not improve, since switching medication or adjusting the dose can often help. There is one important safety point to know early on: the NHS warns that some people may have suicidal thoughts or an urge to self-harm when they start taking an antidepressant. This is more likely in the first weeks and in younger people, which is why close monitoring early in treatment matters. Contact a professional right away, or call or text 988 (US Suicide & Crisis Lifeline), if your mood worsens or you have new thoughts of harming yourself.

Safety and stopping safely

Antidepressants are safest when taken as prescribed and reviewed regularly. Do not change your dose or stop on your own, even once you feel better. The NIMH advises that people should not stop taking a prescribed medication without the help of a health care provider, who can adjust the plan to slowly and safely decrease the dose, and notes that stopping too soon can cause unpleasant or harmful effects.

Stopping suddenly can cause discontinuation symptoms. The NHS describes withdrawal effects such as dizziness, flu-like feelings, nausea, irritability, sleep problems, and brief electric-shock sensations sometimes called "brain zaps." These usually begin within a few days of cutting down and last a few weeks. When it is time to stop, a prescriber will normally taper the dose gradually, sometimes over several weeks or months, to keep these effects mild. Always discuss any plan to start, change, or stop an antidepressant with the professional who prescribed it.

Frequently asked questions

Related conditions

• DepressionPrimary use
• AnxietyCommonly treated
• OCDResponds to SSRIs

References

• National Institute of Mental Health (NIMH) — Mental Health Medications
• National Health Service (NHS) — Overview: Antidepressants
• MedlinePlus, US National Library of Medicine — Antidepressants
• NIMH — Major Depression Statistics