Selective serotonin reuptake inhibitors (SSRIs) 


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Media last reviewed: 09/04/2014

Next review due: 09/04/2016

Types of SSRIs

There are currently six SSRIs prescribed in the UK:

Selective serotonin reuptake inhibitors (SSRIs) are a widely used type of antidepressant medication.

They are mainly prescribed to treat depression, particularly persistent or severe cases, and are often used in combination with a talking therapy such as cognitive behavioural therapy (CBT).

SSRIs are usually the first choice medication for depression because they generally have fewer side effects than most other types of antidepressant.

As well as depression, SSRIs can be used to treat certain other mental health conditions, including:

SSRIs can also be used to treat people with certain other conditions, such as premature ejaculationpremenstrual syndrome (PMS), fibromyalgia and irritable bowel syndrome (IBS).

How they work

It's thought that SSRIs work by increasing the levels of a chemical called serotonin in the brain.

Serotonin is a neurotransmitter (a messenger chemical that carries signals between nerve cells in the brain). It's thought to have a good influence on mood, emotion and sleep.

After carrying a message, serotonin is usually reabsorbed by the nerve cells (known as 'reuptake'). SSRIs work by blocking ('inhibiting') reuptake, meaning more serotonin is available to pass further messages between nearby nerve cells.

It would be too simplistic to say that depression and related mental health conditions are caused by low serotonin levels, but a rise in serotonin levels can improve symptoms and make people more responsive to other types of treatment, such as CBT.

Doses and duration of treatment

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

SSRIs usually need to be taken for two to four weeks before the benefit is felt. You may experience mild side effects early on, but it's important you don't stop taking the medication. These effects will usually wear off quickly.

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

A course of treatment usually lasts for at least six months, although longer courses are sometimes recommended and some people with recurrent problems may be advised to take them indefinitely.

Read more about SSRI doses.

Things to consider

SSRIs are not suitable for everyone. They are not usually recommended if you are pregnant, breastfeeding or under 18 because there is an increased risk of serious side effects, although exceptions can be made if the benefits of treatment are thought to outweigh the risks.

SSRIs also need to be used with caution if you have certain underlying health problems, including diabetesepilepsy and kidney disease.

Some SSRIs can react unpredictably with other medicines, including some over the counter painkillers and herbal remedies such as St John’s wort. Always read the information leaflet that comes with your SSRI medication to check if there are any medications you need to avoid.

Read more about the cautions and interactions of SSRIs.

Side effects

Most people will only experience a few mild side effects when taking SSRIs. These can be troublesome at first, but most will generally improve with time.

Common side effects of SSRIs can include:

  • feeling agitated, shaky or anxious
  • feeling or being sick
  • dizziness
  • blurred vision
  • low sex drive
  • difficulty achieving orgasm during sex or masturbation
  • in men, difficulty obtaining or maintaining an erection (erectile dysfunction)

You will usually see your doctor every few weeks when you first start taking SSRIs, to discuss how well the medication is working. However, you can contact your doctor at any point if you experience any troublesome or persistent side effects.

Read more about the side effects of SSRIs.

Page last reviewed: 10/03/2014

Next review due: 10/03/2016


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The 8 comments posted are personal views. Any information they give has not been checked and may not be accurate.

Hayley1994 said on 26 December 2013

Last thursday, I was prescribed 50mg sertraline by the dr i went to see about intrusive thoughts. I took one and it made me so tired and i slept until 2am and woke up feeling terrible, feeling sick dizzy, dry mouth etc, i didnt take anymore. Since then i have been feeling very ill, i started to get chest pains over the weekend and my heart rate was so abnormally bad i had an ambulance from nhs direct to come, they looked at my blood pressure but it was normal, they then found i had low blood sugar which i think was an affect from the sertraline tablet. I stopped eating much after finding out i had low blood sugar and dont know what it is at right now. I have started to get bad pins and needles in my feet , muscle pain in my legs, bruises all over my legs that have started to appear, tingles in my fingers and hands and feet that have got to a point where if i touch anything they will tingle more at times. I have shivering inside my body for no reason, been shaking alot, constantly tired, breathing difficulties. i am getting dizzy spells alot and my thinking has become a big problem, i am starting to have memory problems, not been able to concentrate , feeling like im unreal and everything around me is a weird crazy dream, basically brain fog like symptoms, im unable to sleep cuz of weird daydreams and noises, my mind has become sensitive to sound, i get hot sweats up my neck and scalp, my hands and feet are cold all the time. my brain is in a mess :( i don't know if the sertraline caused this or the low blood sugar or both! also ive become very irritable, quick tempered and cry alot now :( i feel trapped in my mind and feel that ill never get to the bottom of it and i will have to live with it for the rest of my life and its getting worse :( i want my life back that i had before taking the sertraline tablet :'( if anyone has any thought to what it is im going through please comment, im so scared :./

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rollingwaves said on 21 December 2013

I've taken SSRIs for many years but have recently come to question their usefulness and stopped taking them. I'm particularly uneasy with the kind of longer term use I have been encouraged to adopt (by psychiatrists and GPs). Look up tardive dysphoria to help make your own more informed decisions. My own view is that they are likely to be over prescribed.

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wellnesspharmacist said on 17 October 2013

Alongside the traditional treatment of medical conditions there is much we can do to help ourselves. I found this article really interesting and thought I might share here

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johnthe counsellor said on 29 August 2013

A quick question. is it likely that a person receiving counselling, who is recovering and feeling better about themselves, would have increased serotonin levels ?

If yes, and they are on serotonin based medications, should they in consultation with the doctor reduce those medications to avoid serotonin syndrome ?

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medusacadenza said on 03 August 2013

Doctors and the public are being misled about SSRI's and other widely prescribed psychiatric drugs. This is the problem with evidence based instead of data based medicine.

There are conditions that can be caused by "antidepressant" drugs such as PSSD (Post SSRI Sexual Dysfunction) - This is almost a kind of syndrome in which the person has no libido or emotions and life feels irrelevant to them.

A doctor is supposed to "Do no harm".

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fjr said on 22 December 2012

You state that for most people the sexual side effects improve with time, but no guidance is offered for those people whose side effects persist even after discontinuation.

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User732834 said on 14 December 2012

Selective serotonin reuptake inhibitors have a lot of question marks......we know so little about them, but we sale and prescribe them like bananas. I recommend before taking ssris to inform very well on serotonin, and see just after you understand what are the solutions for you!

A good article on serotonin:

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tpws said on 19 October 2011

Hi, I am taking Citalopram but one of the side effects is that it exsaperates my restless legs, not as bad as Fluoxetine.

Is there one that will not have this side effect ????

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