What are antidepressants?
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:
- obsessive-compulsive disorder (OCD)
- generalised anxiety disorder (GAD)
- post-traumatic stress disorder (PTSD)
Antidepressants are also sometimes used to treat people with long-term (chronic) pain.
Read more about when antidepressants are used.
How antidepressants work
It's 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 don't always address its causes. This is why they're 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're 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 most people do benefit from antidepressants, even if it's sometimes a result of the placebo effect.
Doses and duration of treatment
Antidepressants are usually taken in tablet form. When they're prescribed, you'll start on the lowest possible dose thought necessary to improve your symptoms.
Antidepressants usually need to be taken for 2 to 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 to 6 weeks without feeling any benefit, speak to your doctor or mental health specialist. They may recommend increasing your dose or trying an alternative medication.
A course of treatment usually lasts for 6 months, although a 2-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.
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:
- feeling sick
- dry mouth
- slight blurring of vision
- problems sleeping (insomnia)
- sexual dysfunction, such as erectile dysfunction in men or difficulty achieving orgasm
Side effects should improve within a few days or weeks of treatment as the body gets used to the medication.
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'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) and sertraline (Lustral).
Serotonin-adrenaline 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're 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 who fail 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 when 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.
Side-effects of antidepressants
The side effects of antidepressants can cause problems at first but then generally improve with time.
It's important to persist with treatment, even if you're affected by side effects, as it will take several weeks before you begin to benefit from treatment. With time you should find the benefits of treatment outweigh any problems from side effects.
During the first few months of treatment, you'll usually see your doctor or a specialist nurse at least once every 2 to 4 weeks to see how well the medication is working.
Some of the more common side effects of the main types of antidepressants are outlined below. For more information about the side effects of your specific medication, see the patient information leaflet that comes with it.
SSRIs and SNRIs
Common side effects of selective serotonin reuptake inhibitors (SSRIs) and serotonin-noradrenaline reuptake inhibitors (SNRIs) can include:
- feeling agitated, shaky or anxious
- feeling and being sick
- indigestion and stomach aches
- diarrhoea or constipation
- loss of appetite
- not sleeping well (insomnia), or feeling very sleepy
- low sex drive
- difficulties achieving orgasm during sex or masturbation
- in men, difficulties obtaining or maintaining an erection (erectile dysfunction)
These side effects should improve within a few weeks, although some can occasionally persist.
Tricyclic antidepressants (TCAs)
Common side effects of tricyclic antidepressants (TCAs) can include:
- dry mouth
- slight blurring of vision
- problems passing urine
- weight gain
- excessive sweating (especially at night)
- heart rhythm problems, such as 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.
Common side effects of monoamine oxidase inhibitors (MAOIs) can include:
- dry mouth
- dizziness (particularly after sudden movements, such as standing up quickly)
- feeling sick
- tiredness and difficulty sleeping
In rare cases, MAOIs have the potential to cause a wide range of other side effects. You should check with your doctor or mental health specialist if you're concerned about any unusual symptoms that you have.
There have been cases where MAOIs have caused a dangerous rise in blood pressure. This can cause symptoms such as:
- a stiff neck
- severe headache
- chest pains
- feeling or being sick
- an abnormally fast heartbeat
If you experience a combination of symptoms listed above, seek emergency medical help immediately by dialling for an ambulance.
Potential health risks
Serotonin syndrome is an uncommon, but potentially serious, set of side effects linked to SSRIs and SNRIs.
Serotonin syndrome occurs when the levels of a chemical called serotonin in your brain become too high. It is usually triggered when you take an SSRI or SNRI in combination with another medication (or substance) that also raises serotonin levels, such as another antidepressant or St John’s Wort.
Symptoms of serotonin syndrome can include:
- muscle twitching
If you experience the symptoms listed above, you should stop taking the medication and seek immediate advice from your doctor or specialist. If this is not possible, call NHS 111.
Symptoms of severe serotonin syndrome include:
- a very high temperature (fever)
- seizures (fits)
- irregular heartbeat (arrhythmia)
If you experience symptoms of severe serotonin syndrome, seek emergency medical help immediately by dialling for an ambulance.
Elderly people who take antidepressants, particularly those who take SSRIs, may experience a severe fall in sodium (salt) levels known as hyponatraemia. This may lead to a build-up of fluid inside the cells of the body, which can be potentially dangerous.
This side effect can occur as SSRIs can block the effects of a hormone that helps regulate levels of sodium and fluid in the body. Elderly people are vulnerable because fluid levels become more difficult for the body to regulate.
Mild hyponatraemia can cause symptoms similar to depression or side effects of antidepressants, such as:
- feeling sick
- muscle pain
- reduced appetite
More severe hyponatraemia can cause the following symptoms:
- feeling listless and tired
- psychosis (being unable to tell the difference between reality and your imagination)
- seizures (fits)
The most serious cases of hyponatraemia can cause you to stop breathing or enter a coma.
If you suspect that you, or someone in your care, has mild hyponatraemia you should call your doctor for advice and stop taking SSRIs for the time being.
If you suspect severe hyponatraemia, call for an ambulance.
Hyponatraemia can be treated by feeding a sodium solution into the body through an intravenous drip.
Long-term use of SSRIs and TCAs has been linked to an increased risk of developing type 2 diabetes, although it's not clear if the use of these antidepressants causes diabetes to develop directly.
It may be that the weight gain some people using antidepressants experience increases the risk of them developing type 2 diabetes.
Some people experience suicidal thoughts and a desire to when they first take antidepressants. Young people under 25 seem to be particularly at risk.
Contact your doctor, or go to hospital immediately, if you have thoughts of killing or harming yourself at any time while you're taking antidepressants.
It may be useful to tell a relative or close friend you have started taking antidepressants and ask them to read the leaflet that comes with your medication. You should then ask them to tell you if they think your symptoms are getting worse, or if they're worried about changes in your behaviour.
Alternatives to antidepressants
There are several treatments that can be used as alternatives to antidepressants for treating depression and other mental health conditions.
Cognitive behavioural therapy
Cognitive behavioural therapy (CBT) is a type of talking therapy that's 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.
But if you're unable or unwilling to take antidepressants then you have the option of receiving CBT as a sole treatment.
CBT helps you understand your thoughts and behaviour and how they affect you. It helps you recognise that events in your past may have shaped you, but it concentrates mostly on how you can change the way you think, feel and behave in the present. It also teaches you how to overcome negative thoughts.
CBT is usually available on the NHS, although the waiting lists are usually long. You normally have a short course of sessions, usually 6 to 8 sessions, over 10 to 12 weeks on a one-to-one basis with a therapist trained in CBT. In some cases, you may be offered group CBT.
Computerised CBT is a form of CBT that takes place through a computer screen, rather than face-to-face with a therapist.
These therapies can be prescribed by your doctor or a mental health specialist and are carried out with their advice and support.
Interpersonal therapy (IPT)
Interpersonal therapy (IPT) focuses on your relationships with other people and on problems you may be having in your relationships, such as difficulties with communication or coping with bereavement.
A course of IPT is usually structured in the same way as a course of CBT.
There's some evidence that IPT can be as effective as antidepressants or CBT, but more research is needed.
Counselling is a form of therapy that helps you think about the problems you're experiencing in your life to find new ways of dealing with them. Counsellors support you in finding solutions to problems but don't tell you what to do.
Counselling is ideal for people who are healthy but need help coping with a current crisis, such as anger, relationship issues, bereavement, redundancy, infertility or the onset of a serious illness.
Research suggests that regular exercise may be a more effective treatment for mild depression than antidepressants.
Exercise helps boost levels of chemicals called 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 doctor may refer you to a qualified fitness trainer for an exercise scheme.
Talking through your feelings can be helpful. You can either talk to a friend or relative, or you can ask your doctor to suggest a local self-help group. There are also a number of chat rooms on the internet that offer support.
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 2 types of lithium – lithium carbonate and lithium citrate. Both are usually effective, but if you're 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 3 months to check your lithium levels while you're taking it.
You'll also need to avoid eating a low-salt diet because this can also cause the lithium to become toxic. Ask your doctor for advice about your diet.
Side effects of lithium include:
- dry mouth
- a metallic taste in your mouth
- some mild shaking of your hands
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's usually given twice a week for 3 to 6 weeks.
It's not exactly clear how ECT works, but recent studies suggest it may help reduce connections in an area of the brain linked to depression.
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.
Cautions of antidepressants
There are several important things to consider when taking antidepressants. You should discuss these with your doctor or mental health professional.
Interactions with other medications
Antidepressants can react unpredictably with other medications, including over-the-counter medications such as ibuprofen. Always carefully read the patient information leaflet that comes with your medication to see if there are any medications you should avoid.
If in doubt, your pharmacist or doctor should be able to advise you.
As a precaution, antidepressants are not 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 treatment with antidepressants with the doctor in charge of your care.
If antidepressants are recommended they'll usually be a type called a selective serotonin reuptake inhibitor (SSRI), such as fluoxetine.
As a precaution, the use of antidepressants if you are breastfeeding is not usually recommended.
But 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 is not usually recommended in children and young people under the age of 18. This is because there's evidence that 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 are 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. Many alcoholic drinks also contain the protein tyramine (see below), which can cause a dangerous rise in blood pressure if you are taking an MAOI.
You're less likely to experience unpleasant or unpredictable effects if you drink alcohol while taking a selective serotonin reuptake inhibitor (SSRI) or a serotonin-noradrenaline reuptake inhibitor (SNRI) antidepressant, but avoiding alcohol is often still recommended in these cases.
The use of illegal drugs is not recommended if you're taking antidepressants, particularly if you've been prescribed an MAOI or 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)
As with alcohol, illegal drugs can make symptoms of depression or other mental health conditions worse.
You should never take two different types of antidepressants, such as a TCA and an MAOI, 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
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 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 are 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
Selective serotonin reuptake inhibitors (SSRIs) may not be suitable for you if you have:
- bipolar disorder (alternating bouts of depression and mania) and you're in a manic phase (a period of extremely excitable mood), although they can be useful for depressive phases
- a bleeding disorder, or if you are taking medicines that make it more likely that you may bleed (for example, warfarin)
- type 1 diabetes and type 2 diabetes
- epilepsy – SSRIs should only be taken if your epilepsy is well controlled, and the medication should be stopped if your epilepsy gets worse
- kidney disease
Serotonin-noradrenaline reuptake inhibitors (SNRIs) may not be suitable for you if you have a history of heart disease or you have poorly controlled high blood pressure.
Tricyclic antidepressants (TCAs) may not be suitable for you if you have:
- a history of heart disease
- recently had a heart attack
- liver disease
- an inherited blood disorder called porphyria
- bipolar disorder
- 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
Although they're not commonly prescribed nowadays, monoamine oxidase inhibitors (MAOI) may not be suitable for you if you have:
- a history of heart disease
- liver disease
- bipolar disorder
- an overactive thyroid gland
- had a stroke, or another condition that affects the blood supply to the brain
Another important consideration when taking MAOIs is the need to avoid any food or drink containing a type of protein called tyramine. This is because an MAOI can disrupt the body’s ability to break down tyramine and high levels of tyramine can cause a sudden and dangerous rise in blood pressure.
Examples of food containing tyramine include cheese, yeast extract (such as Marmite) and some salted or pickled meats. Ask for a detailed list of foods and drinks to avoid when you're first prescribed your medication.
MAOIs can also react unpredictably to some anaesthetics and sedatives, so you may be advised to stop taking your medication 2 weeks before having surgery or major dental treatment that requires sedation.
Dosage of antidepressants
When prescribing antidepressants your doctor will usually select the lowest possible dose thought necessary to improve your symptoms.
This approach is intended to reduce the risk of side effects. If this dose proves ineffective, 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 1 to 3 tablets a day.
It usually takes between 2 and 4 weeks before you begin to notice the effects of antidepressants. Contact your doctor if you haven't noticed any improvement after 4 to 6 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 6 months to prevent your condition from recurring when you stop. However, if you've experienced previous episodes of depression, a 2-year course may be recommended and some people with recurrent illness are advised to carry on taking medication indefinitely.
The recommended course of treatment depends largely on the benefits experienced balanced against the side effects of the medication. 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, then continued treatment will not be recommended.
Missed or extra doses
It's important to try 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 which case you should just skip the missed dose. Don't take a double dose in order to ‘make up’ for the one you missed.
If you take more tablets than prescribed, contact your doctor as soon as possible for advice. If this isn't possible, contact your local out of hours service, or call NHS 111. Taking a double dose is unlikely to be harmful, but you should only do it if advised by a medical professional.
You should not suddenly stop taking antidepressants, even if you feel better. Stopping suddenly can lead to withdrawal symptoms such as:
- stomach upsets
- flu-like symptoms
- sensations in the body that feel like electric shocks
- seizures (fits)
Stopping antidepressants too soon can cause your condition to recur and stopping before 3 to 4 weeks may mean the medication has not yet had a chance to take effect.
If your doctor or mental health specialist decides to stop your course of antidepressants, they'll reduce the dose gradually over a few weeks.
What are antidepressants used for?
The main use for antidepressants is treating depression. They're also used for other mental health conditions and treatment of long-term pain.
In most cases, people with moderate to severe depression are given antidepressants as the 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) will usually be prescribed. If your symptoms haven't improved after about 4 weeks, an alternative antidepressant may be recommended or your dose may be increased.
Many antidepressants can be prescribed by your doctor, but there are some types that can only be used under the supervision of a mental health professional. If the depression doesn't respond to simple antidepressant medication, specialists often use other treatments (such as CBT) along with the medication to help achieve better results. They may also give higher doses of the medication.
Other mental health conditions
Antidepressants can also be used to help treat other mental health conditions, including:
- anxiety disorder
- obsessive compulsive disorder (OCD)
- panic disorder
- serious phobias, such as agoraphobia and social phobia
- post-traumatic stress disorder (PTSD)
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.
Even though a type of antidepressant called tricyclic antidepressants (TCAs) was not 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:
- complex regional pain syndrome
- peripheral neuropathy
- multiple sclerosis
- conditions where a nerve becomes trapped, such as sciatica
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.