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What Are Antidepressants?

This information is for anyone who wants to know more about antidepressants. It discusses how they work, why they are prescribed, the many different types of antidepressants and lists their effects and some of their common side-effects.

Always be sure to consult your GP or other qualified medical practitioner if you have questions about your own medication as this guide is not intended to be a substitute for proper medical advice.

Take a look below to learn more about antidepressants, and the role they play in assisting treatment for mental health conditions.


Many people believe that antidepressants are used only in the treatment of depression, however, they can also be used to treat a variety of other conditions, including (but not limited to):

  • Obsessive Compulsive Disorder (OCD)
  • Post-Traumatic Stress Disorder (PTSD)
  • Generalised Anxiety Disorder (GAD)
  • Social Phobia/Social Anxiety
  • Panic Disorder
  • Agoraphobia
  • Treatment of chronic pain conditions eg: sciatica, complex regional pain syndrome and multiple sclerosis.

Neurotransmitters transmit signals and messages throughout the body. Antidepressants work by increasing the number of neurotransmitters in the brain. Serotonin and noradrenaline are involved with mood and emotion, and so it is thought that antidepressants improve or alter the function of these neurotransmitters.

Antidepressants can disrupt the pain signals sent throughout the body, which explains why they can be used in treatment for chronic pain conditions.

When an antidepressant medication is to be prescribed, the first option usually recommended is an ‘SSRI’. This stands for Selective Serotonin Reuptake Inhibitor. They are believed to increase the amount of serotonin (a neurotransmitter) in parts of the brain. It is believed that this helps treat depression. The other main types of ADMs are Tricyclics and Monoamine Oxidase Inhibitors (MAOIs). Tricyclics are the older style of antidepressants. They are still sometimes used, but not so much, due to their higher incidence of side-effects, including being highly toxic in overdose. Like Tricyclics, MAOI’s are not the first choice of antidepressant medications to be used due to their side-effect profile and risks of dangerous interactions with certain food substances.

The most commonly prescribed ADM’s include the SSRIs Citalopram, Fluoxetine (also known as Prozac), Paroxetine (although less so these days) and Sertraline. It is also quite common to see Mirtazapine and Venlafaxine ADMs prescribed. These are not technically SSRIs, but are more similar to SSRIs than they are to Tricyclics and MAOIs. As mentioned above, you may well have been prescribed an SSRI to treat your anxiety disorder such as OCD, GAD, Social Anxiety, PTSD, Panic or Agoraphobia.

Other antidepressants you may have heard of include Amitriptyline and Clomipramine (Tricyclics), Moclobemide (MAOI) and also Duloxetine and Trazadone. There are many others.

They are normally prescribed for people whose depression is of at least ‘moderate intensity’, although it is possible to have them prescribed for depression of a lower intensity, including low levels of persistent depressive symptoms over the course of at least 2 years. This is known as dysthymia.

Official NHS guidance is to offer alternative treatments in the first instance for ‘mild’ depression, including CBT or other psychological treatments.


You may not know that there are actually different types of antidepressants, which can all be used to treat a range of conditions and symptoms. Here, we will explore these in more detail.

Selective Serotonin Reuptake Inhibitors (SSRI’s)

These are probably the most well known and widely prescribed of the antidepressant family. They are well trusted, as they have over 30 years worth of experience in patients. These work – as the name suggests – by blocking the nerve from taking the serotonin back, therefore it prolongs its action in the brain. One of the reasons why these are a popular category of antidepressant is that they are generally easier to tolerate by patients because they tend to have low levels of side effects. Also, incidences of overdose are far less likely to be fatal. Antidepressants which fall into this category are: Citalopram, Escitalopram, Paroxetine, Fluoxetine, Sertraline, Fluvoxamine.

Serotonin-Noradrenaline Reuptake Inhibitors (SNRI’s)

This category of antidepressants was originally designed to be more effective than SSRI’s. This is because not only does it prevent the re-uptake of serotonin, but it also blocks the re-uptake of noradrenaline. However, the evidence that this has been the case is uncertain. Some people react better to SSRI treatment, whereas others react better to SNRI treatment. Antidepressants which fall into this category are: Duloxetine and Venlafaxine.

Tricyclic Antidepressants (TCA’s)

TCA’s are typically no longer recommended as the ‘first line’ antidepressant, as they display more risks in the incidence of overdose. It is also reported that patients can suffer badly with the side effects from these. However, they can be used for patients who haven’t responded well to other types of treatment or who have very severe depression. Antidepressants which fall into this category are: Amitriptyline, Nortriptyline, Clomipramine, Imipramine, Lofepramine, Dosulepin, Doxepin, Trimipramine.

Monoamine Oxidase Inhibitors (MAOI’s)

These are another older type of antidepressant, which are not the first port of call for treatment. Similarly to TCA’s, these are only really used if the patient hasn’t responded well to other treatments or other categories of antidepressant. These should also only be taken under supervision of a psychiatrist. They work to block the activity of the monoamine oxidase enzyme, which breaks down serotonin and noradrenaline neurotransmitters. There is another difficulty in taking these medications, as certain foods need to be avoided as they can interact with them. On the other hand, some people have success with this category of antidepressant. Antidepressants which fall into this category are: Isocarboxazid, Phenelzine, Moclobemide and Tranylcypromine.


There are some antidepressants which don’t really fit into any category. These include: Agomelatine, Triptafen, Mirtazapine and Trazodone.

You may not know that there are many ways that antidepressants can be administered. Antidepressants do not only come in tablet form. They can also be taken as capsules, in liquid form, oral drops and in the form of a dispersible tablet (which dissolves in water).


The best thing to do when starting a new medication is to listen carefully to the advice that your doctor and pharmacist gives you, and then to read the patient information leaflet thoroughly, as this will give you the most in depth and specific information possible.

Some common side effects which are noticed within the first few weeks of beginning a new antidepressant can include (but are not limited to):

  • Nausea/feeling sick
  • Having a dry mouth
  • Difficulty in sleeping (insomnia)
  • Sexual dysfunction
  • Becoming unusually dizzy
  • Constipation
  • Blurring of the vision
  • Suicidal feelings

The latter can look very alarming, and you would imagine could be the last side effect in the world to be associated with an antidepressant. There is some debate as to why this may happen. But if it does, it is important that if you feel in imminent danger because of suicidal thoughts, you call 999 or go to your nearest A&E department.

For the majority of people, most side effects will pass after around a month on the new medication. It is generally recommended by GP’s to stick with a medication for at least 4-6 weeks, as it is only then that it will be taking it’s full effect and your body will be getting used to it’s changes. It is always best to contact your GP/mental health professional if you have any worries about your medication or side effects.

Amitriptyline – Sedation, constipation, dry mouth, weight gain

Citalopram, Fluoxetine and Sertraline – Gastric disturbance, headache, insomnia, sexual dysfunction

Mirtazapine – Sedation and weight gain

Venlafaxine – Nausea, headache, sedation, dizziness, sexual dysfunction, sleep disturbance, low blood pressure, weight gain 


It is very, very important that you speak to your GP or a mental health professional if you feel for whatever reason you wish to stop taking your medication. With some medications, you can be hit with tough side effects through withdrawing too quickly, or stopping your medication ‘cold turkey’. If you try to come off your medication on your own, you may risk your symptoms coming back or potentially risk your health.

Your healthcare professional will discuss your options with you. They could suggest a range of things, including; altering the dose of your current medication, giving you extra temporary medication to help you wean off if you are struggling with the ‘half life’ of your medication, weaning off your current medication with the view of trying a new medication, or simply weaning off medication all together. This will all depend on your individual circumstances, as everybody’s mental health is different.

All antidepressants have the potential to cause some withdrawal problems if they have been taken for 6 weeks or longer. They should not be stopped abruptly. Unfortunately some people do stop taking them as soon as they feel better and put themselves at risk of withdrawal problems and/or relapse.

Prescribing guidance states that reducing antidepressant medication doses should be tapered over a period of at least 4 weeks.

NHS guidance also states that antidepressant medications should be continued for 6-9 months after symptoms of depression lift to reduce the chance of further depressive episodes in the future. This is not a guarantee of not becoming depressed again, and neither does it mean someone needs to stay on antidepressants indefinitely if their depression lifts.


NICE Guidelines

(search for depression and the anxiety disorders)

Maudsley Prescribing Guidelines, 11th edition (2012)

Choice and Medication

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Written by Anxiety United

Anxiety United created by Billy Cross is a free to use platform sharing resources, advice and videos relating to Anxiety & Mental Health.

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