About antidepressants

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

They can also be used to treat some other conditions, including:

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

How antidepressants work

It's thought that antidepressants work by increasing neurotransmitters. These are chemicals in the brain like serotonin and noradrenaline. They can improve mood and emotion, although this process isn't fully understood.

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

While antidepressants can treat the symptoms of depression, they don't always address its causes. This is why they're usually used in combination with therapy. This helps to treat more severe depression or other mental health conditions.

Types of antidepressants

There are different types of antidepressants.

Selective serotonin reuptake inhibitors (SSRIs)

SSRIs are the most widely prescribed antidepressant. They're 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-noradrenaline reuptake inhibitors (SNRIs)

SNRIs are similar to SSRIs. They were designed to be a more effective antidepressant than SSRIs. However, evidence suggests that some people respond better to SSRIs, while others respond better to SNRIs.

Examples of SNRIs include:

  • duloxetine (Cymbalta and Yentreve)
  • 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 like those of SSRIs, but they're thought to cause fewer sexual problems. They may also cause more drowsiness at first.

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

Tricyclic antidepressants (TCAs)

TCAs are an older type of antidepressant. They're no longer usually recommended as a first-line treatment for depression. This is 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 for people with severe depression who fail to respond to other treatments. TCAs may also be recommended for other mental health conditions, like OCD and bipolar disorder.

Examples of TCAs include:

  • amitriptyline (Tryptizol)
  • clomipramine (Anafranil)
  • imipramine (Tofranil)
  • lofepramine (Gamanil)
  • nortriptyline (Allegron)

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

Accessing medicines self-help guide

Visit our self-help guide on accessing medicines if you have difficulty getting the medicines you need.

Self-help guide: Accessing medicines

How effective are antidepressants?

Antidepressants can be helpful for people with moderate or severe depression. They're the most effective treatment for relieving symptoms quickly, particularly in severe depression.

Doses and duration of treatment

Antidepressants are usually taken in tablet form. You'll usually have to take 1 to 3 tablets a day. The exact number of tablets you'll take will depend on the:

  • type of antidepressant you're prescribed
  • severity of your depression

If you're prescribed antidepressants, you'll usually start on a low dose.

Antidepressants usually need to be taken for around 7 to 14 days (without missing a dose) before the benefits are felt.

It's important that you don't stop taking your antidepressants if you get some mild side effects early on. These effects usually wear off quickly.

If you take an antidepressant for 4 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 6 months. Some people with recurrent depression may be advised to take them indefinitely.

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 a dose, 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.

You should not take more than your prescribed dose unless advised by your doctor or prescriber. If you do take an extra dose by mistake, you should check with your pharmacist or medical professional for advice, or phone 111.

Stopping antidepressants 

You shouldn't suddenly stop taking antidepressants, even if you feel better. Stopping suddenly can lead to withdrawal symptoms, like:

Coming off antidepressants too soon can cause your condition to return. Stopping before you have been taking antidepressants for 3 to 4 weeks may mean the medication hasn't had a chance to take effect.

Antidepressants should not be stopped suddenly. If your GP or mental health specialist decides to stop your antidepressants, they'll reduce the dose gradually over a few weeks.

When antidepressants are used

Antidepressants are mostly used to treat clinical depression in adults. They're also used for other mental health conditions and for treating long-term pain.

Antidepressants for depression

Most adults with moderate to severe depression are treated with antidepressants first. They're often prescribed with a talking therapy like cognitive behavioural therapy (CBT). CBT is a type of therapy that uses problem-solving to help improve thought, mood and behaviour.

An antidepressant called a selective serotonin reuptake inhibitor (SSRI) is usually prescribed first. If your symptoms don't improve after 4 weeks, you may be given a different antidepressant. Your dose could also be increased.

Many antidepressants can be prescribed by your GP. However, some types can only be used under the care of a mental health professional.

Antidepressants aren't always recommended for mild depression. This is because research has found that they may be less effective for mild depression.

However, antidepressants are sometimes prescribed for a few months for mild depression. This is to see if symptoms improve. If there are no benefits in this time, the medication will be slowly withdrawn.

Antidepressants for children and young people

Children and young people with moderate to severe depression should be offered a course of psychotherapy before antidepressants. This treatment should last at least 3 months.

In some cases, an SSRI called fluoxetine may be offered to young people aged 12 to 18. This should be offered in combination with psychotherapy.

Antidepressants for other mental health conditions

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

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

Using antidepressants for long-term pain

Chronic nerve pain, also known as neuropathic pain, is caused by nerve damage or problems with the nerves. It’s often unresponsive to traditional painkillers like paracetamol.

Tricyclic antidepressants (TCAs) may help to treat some chronic (long-term) nerve pain.

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

Antidepressants have also been used to treat chronic pain that doesn’t involve nerves (non-neuropathic pain). This includes:

However, they're thought to be less effective for this purpose.

As well as TCAs, SSRIs and serotonin-noradrenaline reuptake inhibitors (SNRIs) can be used to treat chronic non-neuropathic pain.

Bedwetting in children

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

Alternatives to antidepressants

There are alternatives to antidepressants. These may be used to manage depression and other mental health conditions. This includes talking therapies like:

  • cognitive behavioural therapy (CBT)
  • interpersonal therapy (IPT)
  • counselling
  • self-help groups

Other alternatives to antidepressants that may be recommended include:

  • exercise
  • lithium
  • electroconvulsive therapy (ECT)

Cautions and interactions

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

Medications

Antidepressants can react unpredictably with other medications, including over-the-counter medications like ibuprofen. Always read the patient information leaflet that comes with your medication. This will let you know if there are any medications you should avoid.

If in doubt, your pharmacist or GP should be able to advise you.

Pregnancy

As a precaution, antidepressants aren't usually recommended for 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 using antidepressants during pregnancy include:

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

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

Breastfeeding

As a precaution, using antidepressants while 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, 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.

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 like 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.

Alcohol

You should be wary of drinking alcohol if you're taking antidepressants. Alcohol itself is a depressant so it may make your symptoms worse.

If you drink alcohol while taking some types of antidepressants, you may become drowsy and dizzy.

Illegal drugs

The use of illegal drugs isn't recommended if you're taking antidepressants. This is because they can cause unpredictable and unpleasant effects.

In particular, you should avoid taking:

Illegal drugs can make symptoms of depression or other mental health conditions worse.

St John's Wort

St John’s Wort is a popular herbal remedy promoted for the treatment of depression.

While there's evidence of its effectiveness, many experts advise against its use. This is because the active ingredients varies among individual brands and batches. This can make the effects unpredictable.

Taking St John's Wort with other medications can also cause serious health problems.

You shouldn't take St John's Wort if you're pregnant or breastfeeding.

Driving

Some antidepressants can cause dizziness, drowsiness and blurred vision. These symptoms usually happen when you first start taking antidepressants.

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

Other antidepressants

You should never take 2 different types of antidepressants together. This is because taking certain combinations of antidepressants can make you feel very ill. It can also be life-threatening.

If your doctor decides to change your antidepressant, the dose of the first one will usually be gradually reduced before the second is given.

Side effects of antidepressants

Antidepressants can cause side effects at first, but these usually improve with time.

If you experience minor side effects, it's important to continue treatment. This is because it can take several weeks before you begin to benefit from treatment. With time, you should find that the benefits of treatment outweigh any side effects.

During the first few months of treatment, you'll usually see your doctor or a specialist nurse every 2 to 4 weeks. This will let them see how well the medication is working.

If you experience any severe side effects, you should let your specialist know.

For more information about your specific medication, see the patient information leaflet. This will be in the box with your medication.

Side effects of SSRIs and SNRIs

Common side effects of SSRIs and SNRIs can include:

These side effects should improve within a few weeks, although some may persist.

Side effects of TCAs

Common side effects of TCAs can include:

  • dry mouth
  • slight blurring of vision
  • constipation
  • problems passing urine
  • dizziness
  • weight gain
  • excessive sweating (especially at night)
  • heart rhythm problems, like noticeable palpitations or a fast heartbeat (tachycardia)

The side effects should ease after a couple of weeks as your body begins to get used to the medication.

Potential health risks of antidepressants

Your doctor or specialist will explain any potential health risks linked to antidepressants.

Serotonin syndrome

Serotonin syndrome isn't common but it can be serious. It's a set of side effects linked to SSRIs and SNRIs.

Serotonin syndrome occurs when levels of serotonin become too high. Serotonin is a chemical in your brain. It's usually triggered when you take an SSRI or SNRI with another medication (or substance) that also raises serotonin levels. This could be another antidepressant or St John’s Wort.

Symptoms of serotonin syndrome can include:

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

If you experience symptoms of serotonin syndrome, you should stop taking the medication. You should then seek immediate advice from your GP or specialist. If this isn't possible, phone 111.

Urgent advice: Phone 999 if:

You or someone else experiences symptoms of severe serotonin syndrome like:

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

Hyponatraemia

Elderly people who take antidepressants can experience a fall in sodium (salt) levels. This is known as hyponatraemia. This may lead to a build-up of fluid inside the cells of the body which can be dangerous.

SSRIs can block the effects of a hormone that regulates sodium and fluid levels. Elderly people are vulnerable because their fluid levels become more difficult to control.

Mild hyponatraemia can cause symptoms like:

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

If you suspect mild hyponatraemia, you should call your GP. You should also stop taking SSRIs for the time being.

Urgent advice: Phone 999 if:

You or someone else has symptoms of severe hyponatraemia like:

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

The most serious cases of hyponatraemia can cause you to stop breathing or enter a coma.

Diabetes

Long-term use of SSRIs and TCAs has been linked to an increased risk of developing type 2 diabetes. However, it's not clear if the use of these antidepressants directly causes diabetes.

Suicidal thoughts

In rare cases, some people experience suicidal thoughts and a desire to self-harm when they first take antidepressants. Young people under 25 seem particularly at risk.

Contact your GP or go to hospital immediately if you have thoughts of killing or harming yourself.

It may be useful to tell a relative or close friend if you've started taking antidepressants. Ask them to read the leaflet that comes with your medication. Get them to tell you if they think your symptoms are getting worse, or if they're worried about changes in your behaviour.

Last updated:
03 November 2022