Antidepressants are a type of medication used to treat depression or prevent it recurring.

They can also be used to treat a number of other conditions, including:

Antidepressants are also sometimes used to treat people with long-term (chronic) pain.

Read more about when antidepressants are used.

How antidepressants work

It is thought antidepressants work by increasing levels of a group of chemicals in the brain called neurotransmitters. Certain neurotransmitters, such as serotonin and noradrenaline, can improve mood and emotion, although this process is not fully understood.

Increasing levels of neurotransmitters can also disrupt pain signals sent by nerves, which may explain why some antidepressants can help relieve long-term pain.

While antidepressants can help treat the symptoms of depression, they do not always address its causes. This is why they are usually used in combination with therapy to treat more severe depression or other mental health conditions caused by emotional distress.

How effective are antidepressants?

Most people benefit from taking antidepressants to some degree, but research suggests that antidepressants may not be as effective as previously thought in cases of mild depression.

However, they are the most effective treatment in relieving symptoms quickly, particularly in cases of severe depression.

The Royal College of Psychiatrists estimates that 50-65% of people treated with an antidepressant for depression will see an improvement, compared to 25-30% of those taking inactive “dummy” pills (placebo). This means that most people do benefit from antidepressants, even if it is sometimes a result of the placebo effect.

Doses and duration of treatment

Antidepressants are usually taken in tablet form. When they are prescribed, you will start on the lowest possible dose thought necessary to improve your symptoms.

Antidepressants usually need to be taken for 2-4 weeks (without missing a dose) before the benefit is felt. It's important not to stop taking them because you get some mild side effects early on, as these effects will usually wear off quickly.

If you take an antidepressant for 4-6 weeks without feeling any benefit, speak to your GP or mental health specialist. They may recommend increasing your dose or trying an alternative medication.

A course of treatment usually lasts for six months, although a two-year course may be recommended for people with a previous history of depression and some people with recurrent depression may be advised to take them indefinitely.

Read more about antidepressant doses.

Side effects

Different antidepressants can have a range of different side effects. Always check the information leaflet that comes with your medication to see what the possible side effects are. Common side effects of antidepressants in general are usually mild and can include:

Side effects should improve within a few days or weeks of treatment as the body gets used to the medication.

Read more about the side effects of antidepressants and cautions and interactions of antidepressants.

Different types of antidepressants

There are a number of different types of antidepressants. Some of the most widely used types are discussed below.

Selective serotonin reuptake inhibitors (SSRIs)

SSRIs are the most widely prescribed type of antidepressants. They are usually preferred over other antidepressants as they cause fewer side effects. An overdose is also less likely to be serious.

Fluoxetine is probably the best known SSRI (sold under the brand name Prozac). Other SSRIs include citalopram (Cipramil), paroxetine (Seroxat) and sertraline (Lustral).

Serotonin-noradrenaline reuptake inhibitors (SNRIs)

SNRIs are similar to SSRIs. They were designed to be a more effective antidepressant than SSRIs. However, the evidence that SNRIs are more effective in treating depression is uncertain. It seems some people respond better to SSRIs while others respond better to SNRIs.

Examples of SNRIs include duloxetine (Cymbalta and Yentreve) and venlafaxine (Efexor).

Tricyclic antidepressants (TCAs)

Tricyclic antidepressants (TCAs) are an older type of antidepressant. They are no longer usually recommended as a first-line treatment for depression because they can be more dangerous if an overdose is taken. They also cause more unpleasant side effects than SSRIs and SNRIs.

Exceptions are sometimes made in people with severe depression that fails to respond to other treatments. TCAs may also be recommended for other mental health conditions such as obsessive compulsive disorder and bipolar disorder.

Examples of TCAs include amitriptyline (Tryptizol), clomipramine (Anafranil), imipramine (Tofranil), lofepramine (Gamanil) and nortriptyline (Allegron).

Some types of TCAs, such as amitriptyline, can also be used to treat chronic nerve pain.

Monoamine oxidase inhibitors (MAOIs)

Monoamine oxidase inhibitors (MAOIs) are another older type of antidepressant with a wide range of side effects that are rarely used nowadays. They tend only to be used if other types of antidepressants are not effective and should only be taken under the supervision of a psychiatrist.

A significant drawback of MAOIs is the need to avoid certain foods and drinks, such as cheese and pickled fish, which contain a protein called tyramine. This is because consuming tyramine while taking MAOIs can cause a dangerous rise in blood pressure.

Examples of MAOIs include moclobemide (Manerix) and phenelzine (Nardil).

Alternatives to antidepressants

Alternative treatments for depression include talking therapies such as cognitive behavioural therapy (CBT).

Increasingly, people with moderate to severe depression are treated using a combination of antidepressants and CBT. Antidepressants work quickly in reducing symptoms, whereas CBT takes time to deal with causes of depression and ways of overcoming it.

Regular exercise has also been shown to be useful in those with mild depression.

Read more about alternatives to antidepressants.

The Yellow Card Scheme allows you to report suspected side effects from any type of medicine that you are taking. It is run by a medicines safety watchdog called the Medicines and Healthcare products Regulatory Agency (MHRA). See the Yellow Card Scheme website for more information.

Page last reviewed: 01/10/2013

Next review due: 01/10/2015