Antidepressents are a type of medication used to treat Clinical 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 what antidepressants are used for.

How antidepressants work

It is thought that antidepressants work by changing the 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 also help relieve symptoms of long-term (chronic) 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.




Read more about antidepressant doses.

Side effects

In general, the most common side effects of antidepressants are usually mild. 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)

These are the most widely prescribed type of antidepressants.

SSRIs 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)
  • sertraline (Lustral)

Serotonin-norepinephrine 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).

Noradrenaline and specific serotonergic antidepressants (NASSAs)

NASSAs may be effective for some people who are unable to take SSRIs. The side effects of NASSAs are similar to those of SSRIs, but they're thought to cause fewer sexual problems. However, they may also cause more drowsiness at first.

The main NASSA prescribed in the UK is mirtazapine (Zispin).

Tricyclic antidepressants

Tricyclic antidepressants (TCAs) are an older type of antidepressants. 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)
  • nortriptyline (Allegron)

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

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.

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The main use for antidepressants is treating clinical depression in adults. They're also used for other mental health conditions and treatment of long-term pain.

In most cases, adults with moderate to severe depression are given antidepressants as a first form of treatment. They're often prescribed along with a talking therapy such as cognitive behavioural therapy (CBT). CBT is a type of therapy that uses a problem-solving approach to help improve thought, mood and behaviour.

Antidepressants aren't always recommended for treating mild depression because research has found limited effectiveness.

However, antidepressants are sometimes prescribed for a few months for mild depression to see if you experience any improvement in your symptoms. If you don’t see any benefits in this time, the medication will be slowly withdrawn.

Initially, a type of antidepressant called a selective serotonin reuptake inhibitor (SSRI) is usually prescribed. If your symptoms haven't improved after about four weeks, an alternative antidepressant may be recommended or your dose may be increased.

Many antidepressants can be prescribed by your GP, but some types can only be used under the supervision of a mental health professional. If the depression doesn't respond to antidepressant medication alone, other treatments, such as CBT, may also be used to help achieve better results. They may also give higher doses of the medication.

Children and young people

Children and young people with moderate to severe depression should first be offered a course of psychotherapy that lasts for at least three months.

In some cases, an SSRI called fluoxetine may be offered in combination with psychotherapy to treat moderate to severe depression in young people aged 12-18.

Other mental health conditions

Antidepressants can also be used to help treat other mental health conditions, including:

As with depression, SSRIs are usually the first choice of treatment for these conditions. If SSRIs prove ineffective, an alternative type of antidepressant can be used.

Long-term pain

Even though a type of antidepressant called tricyclic antidepressants (TCAs) weren't originally designed to be painkillers, there's evidence to suggest they're effective in treating chronic (long-term) nerve pain in some people.

Chronic nerve pain, also known as neuropathic pain, is caused by nerve damage or other problems with the nerves, and is often unresponsive to traditional painkillers, such as paracetamol.

Amitriptyline is a TCA that's usually used to treat neuropathic pain. Conditions that may benefit from treatment with amitriptyline include:

Antidepressants have also been used to treat cases of chronic pain that don't involve nerves (non-neuropathic pain). However, they're thought to be less effective for this purpose. As well as TCAs, SSRIs and serotonin-noradrenaline reuptake inhibitors (SNRIs) can also be used to treat chronic non-neuropathic pain.

Conditions that cause non-neuropathic pain which may benefit from treatment with antidepressants include fibromyalgia, chronic back pain and chronic neck pain.

Bedwetting in children

TCAs are sometimes used to treat bedwetting in children, as they can help relax the muscles of the bladder. This increases bladder capacity and reduces the urge to urinate.

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There are several important things to consider when taking antidepressants. You should discuss these with your GP or mental health professional.

Interactions with other medications

Antidepressants can react unpredictably with other medications, including over-the-counter medications such as ibuprofen. Always read the patient information leaflet that comes with your medication to see if there are any medications you should avoid.



As a precaution, antidepressants aren't usually recommended for most pregnant women, especially during the early stages of a pregnancy. However, exceptions can be made if the risks posed by depression (or other mental health conditions) outweigh any potential risks of treatment.

Potential complications that have been linked to antidepressant use during pregnancy include:

  • loss of the pregnancy
  • birth defects affecting the baby’s heart (congenital heart disease)
  • a rare condition in newborns called pulmonary hypertension, where the blood pressure inside the lungs is abnormally high, causing breathing difficulties

However, there's no hard evidence that antidepressants cause these complications.

If you're pregnant and depressed, you should discuss the pros and cons of antidepressants with the doctor in charge of your care.

If antidepressants are recommended, they will usually be a type called a selective serotonin reuptake inhibitor (SSRI), such as fluoxetine.


As a precaution, the use of antidepressants if you're breastfeeding isn't usually recommended.

However, there are circumstances when both the benefits of treatment for depression (or other mental health conditions) and the benefits of breastfeeding your baby outweigh the potential risks.

If you're treated with antidepressants when breastfeeding, then paroxetine or sertraline is normally recommended.

Children and young people

The use of antidepressants isn't usually recommended in children and young people under the age of 18. This is because there's evidence that, in rare cases, they can trigger thoughts about suicide and acts of self-harm in this age group.

Concerns have also been raised that their use could affect the development of the brain in children and young people.

An exception can usually only be made if the following points are met:

  • the person being treated has failed to respond to talking therapies such as cognitive behavioural therapy, and
  • the person being treated will continue to receive talking therapies in combination with antidepressants, and
  • the treatment is supervised by a psychiatrist (a doctor who specialises in treating mental health conditions)

If an antidepressant is recommended, then fluoxetine is usually the first choice.


You should be wary of drinking alcohol if you're taking antidepressants, as alcohol is itself a depressant and drinking alcohol can make your symptoms worse.

If you drink alcohol while taking types of antidepressants called tricyclic antidepressants (TCAs) or monoamine oxidase inhibitors (MAOIs), you may become drowsy and dizzy.

You're less likely to experience unpleasant or unpredictable effects if you drink alcohol while taking an SSRI or a serotonin-noradrenaline reuptake inhibitor (SNRI) antidepressant, but avoiding alcohol is often still recommended in these cases.

Illegal drugs

The use of illegal drugs isn't recommended if you're taking antidepressants, particularly if you've been prescribed a TCA. This is because they can cause unpredictable and unpleasant effects.

In particular, you should avoid taking:

  • cannabis – smoking cannabis while taking a TCA can make you feel very ill
  • amphetamines (speed)
  • cocaine
  • heroin
  • ketamine

As with alcohol, illegal drugs can make symptoms of depression or other mental health conditions worse.

Other antidepressants

You should never take two different types of antidepressants, such as an SSRI and a TCA, unless advised by the doctor in charge of your care. This is because taking certain combinations of antidepressants can make you feel very ill and can be life-threatening.

If a decision is taken to switch you from one type to another, the dosage of the first antidepressant will usually be gradually reduced before the second is administered.

St John’s Wort


While there's evidence of its effectiveness, many experts advise against its use, because the amount of active ingredient varies among individual brands and batches, making the effects unpredictable.

Taking St John's Wort with other medications, such as anticonvulsants, anticoagulants, antidepressants and the contraceptive pill, can also cause serious health problems.

You shouldn't take St John's Wort if you're pregnant or breastfeeding, as it's unclear whether it's safe.

Driving and operating machinery

Some antidepressants can cause dizziness, drowsiness and blurred vision, particularly when you first start taking them.

If you do experience these problems, you should avoid driving or using tools and machinery.

Cautions for specific antidepressants:


SSRIs may not be suitable if you have:

  • bipolar disorder and you're in a manic phase (a period where you're extremely excitable), although they can be useful for depressive phases
  • a bleeding disorder, or if you're taking medicines that make it more likely you may bleed (such as warfarin)
  • type 1 diabetes and type 2 diabetes
  • kidney disease


SNRIs may not be suitable if you have a history of heart disease or you have poorly controlled high blood pressure.


TCAs may not be suitable if you have:

  • a history of heart disease
  • recently had a heart attack
  • liver disease
  • an inherited blood disorder called porphyria
  • bipolar disorder
  • schizophrenia
  • a growth on your adrenal glands that is causing high blood pressure (pheochromocytoma)
  • an enlarged prostate gland
  • narrow angle glaucoma – increased pressure in the eye
  • epilepsy
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When prescribing antidepressants, your GP usually selects the lowest possible dose thought necessary to improve your symptoms.

This approach is intended to reduce the risk of side effects. If this dose doesn't work, it can be gradually increased.

Antidepressants are usually taken in tablet form. Depending on the type of antidepressant prescribed and the severity of your depression, you'll usually have to take one to three tablets a day.

It usually takes around seven days before you begin to notice the effects of antidepressants. Contact your doctor if you haven't noticed any improvement after four weeks, as they may recommend increasing your dose or trying an alternative antidepressant.

It's usually recommended that a course of antidepressants lasts at least six months, to prevent your condition recurring when you stop. However, if you've experienced previous episodes of depression, a two-year course may be recommended and some people with recurrent illness are advised to carry on taking medication indefinitely.

The recommended course of treatment largely depends on weighing up the benefits of the medication against the side effects. If your illness is severe and the medication is effective, treatment will often be continued. If your illness is mild and the medication doesn’t help and causes side effects, continued treatment won't be recommended.

Missed or extra doses

It's important not to miss any of your doses, as this could make your treatment less effective.

If you do miss one of your doses, take it as soon as you remember, unless it's almost time to take your next dose. In this case, you should just skip the missed dose. Don't take a double dose to "make up" for the one you missed.

If you take more tablets than prescribed, contact your GP as soon as possible for advice. If this isn't possible, contact your local out of hours service, or call NHS Direct Wales 0n 0845 46 47. Taking a double dose is unlikely to be harmful, but you should only do so if advised by a medical professional.

Stopping antidepressants


  • stomach upsets
  • flu-like symptoms
  • anxiety
  • dizziness
  • sensations in the body that feel like electric shocks
  • seizures (fits)



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Side effects








Tricyclic antidepressants (TCAs)

Common side effects of TCAs can include:


Potential health risks

Serotonin syndrome



Symptoms of serotonin syndrome can include:

  • confusion
  • agitation
  • muscle twitching
  • sweating
  • shivering
  • diarrhoea

If you experience the symptoms listed above, you should stop taking the medication and seek immediate advice from your GP or specialist. If this isn't possible, call NHS Direct Wales on 0845 46 47.

Symptoms of severe serotonin syndrome include:

  • a very high temperature (fever)
  • seizures (fits)
  • irregular heartbeat (arrhythmia)
  • unconsciousness






  • feeling sick
  • headache
  • muscle pain
  • reduced appetite
  • confusion

More severe hyponatraemia can cause the following symptoms:

  • feeling listless and tired
  • disorientation
  • agitation
  • psychosis
  • seizures (fits)









Suicidal thoughts




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There are several treatments that can be used as alternatives to antidepressants for treating depression and other mental health conditions.

Talking therapies

Cognitive behavioural therapy

Cognitive behavioural therapy (CBT) is a type of talking therapy that is increasingly being used in the treatment of depression. Most experts recommend that people with moderate to severe depression are treated with a combination of CBT and antidepressants.

However, if you are unable or unwilling to take antidepressants then you have the option of receiving CBT on its own.


CBT is usually available on the NHS although waiting lists can be long. You normally have a short course of sessions, usually six to eight sessions, over 10-12 weeks on a one-to-one basis with a therapist trained in CBT. In some cases, you may be offered group CBT.

Online CBT


It's delivered in a series of weekly sessions and should be supported by a healthcare professional. For instance, it's usually prescribed by your GP and you may have to use the surgery computer to access the programme.

Interpersonal therapy (IPT)





Counselling is a form of therapy that helps you think about the problems you are experiencing in your life to find new ways of dealing with them. Counsellors support you in finding solutions to problems, but do not tell you what to do.

Counselling on the NHS usually consists of 6-12 sessions lasting an hour each. You talk in confidence to a counsellor. The counsellor supports you and offers practical advice.




Exercise helps boost levels of serotonin and dopamine in the brain, which can lift your mood.

Exercising on a regular basis can boost self-esteem and confidence which can also help relieve symptoms of depression.

Your GP may be able to refer you via the National Exercise Referral Scheme, a partnership with the Local Authorities and the NHS in Wales.

Self-help groups

Talking through your feelings can be helpful. You can either talk to a friend or relative, or you can ask your GP to suggest a local self-help group. The Health Wellbeing and Support local services search is also a useful place to look for self-help groups that are local to you.


If you've tried several different antidepressants and had no improvement, your doctor may offer you a type of medication called lithium, in addition to your current treatment.

There are two types of lithium – lithium carbonate and lithium citrate. Both are usually effective, but if you are taking one that works for you, it's best not to change.

If the level of lithium in your blood becomes too high, it can become toxic. So, you'll need blood tests every three months to check your lithium levels while you're on it.


Side effects of lithium include:

  • dry mouth
  • a metallic taste in your mouth
  • some mild shaking of your hands
  • diarrhoea

These side effects usually pass with time once your body gets used to the medication.

Electric shock treatment

Sometimes a treatment called electroconvulsive therapy (ECT) may be recommended if you have severe depression and other treatments haven't worked as it can be highly effective.

During ECT, you'll first be given an anaesthetic and medication to relax your muscles. Then you'll receive an electric current to your brain through electrodes placed on your head.

You may be given a series of ECT sessions. It is usually given twice a week for 3-6 weeks.


For most people, ECT is good for relieving severe depression, but the beneficial effect tends to wear off after several months. Some people get unpleasant side effects, including short-term headaches, memory problems, nausea and muscle aches. However, these risks need to be balanced against the risks of other treatments and the effects of not treating depression.

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Last Updated: 23/11/2015 09:12:35