Antidepressants

Explains what antidepressants are, how they work, possible side effects and information about withdrawal.

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What side effects can antidepressants cause?

Every antidepressant has the potential to cause particular side effects, and these can vary from drug to drug (for details of the possible side effects of a particular antidepressant, look it up in our antidepressants A–Z).

This page shows which side effects are common to different types of antidepressant, and then gives detailed information about each of these side effects.

Remember that while some side effects are quite common, many of them are rare, and not everyone experiences them.

It's up to you to decide whether or not the antidepressant has more
benefits for you than side effects. (See our page on coping with side effects for more information).

"It took me a long time to take an SSRI, mainly as I was terrified of the side effects listed, but my doctor finally convinced me that my depression was much worse [than the side effects]."

What side effects can be caused by each type of antidepressant?

There are some side effects that are common to all antidepressants of a particular type. These are listed below, by type of antidepressant:

SSRIs and SNRIs

Side effects that all drugs of this type can cause (most common first):

Tricyclic and tricyclic-related antidepressants

Side effects that all drugs of this type can cause (most common first):

MAOIs

Side effects that all drugs of this type can cause (most common first):

For guidance on what to do if you experience a side effect, see our page on coping with side effects.

How might these side effects affect me?

This section gives information explaining how each of the side effects listed above might affect you and your body.

Antimuscarinic effects

Antimuscarinic effects (sometimes called anticholinergic effects) is the medical term for a group of side effects which can occur with many different types of drugs – especially tricyclic antidepressants.

They include:

blurred vision
confusion and agitation
constipation, which may become life-threatening if not treated
difficulty urinating
drowsiness
dry mouth, which can cause tooth decay in the long term
hallucinations
hot or dry skin, and decreased sweating
increased pressure in the eye
low blood pressure (taking hot baths increases this risk)
rapid heartbeat and disturbed heart rhythm
trembling

These side effects can happen because, as well as affecting brain chemicals related to mood, the drug can also affect brain chemicals which control the different functions in your body.

Decreased alertness

Antidepressants can make you feel less alert or able to concentrate. This can affect:

driving
other skilled tasks

Diabetes

Long-term use of antidepressants over several years is associated with an increased risk of diabetes, especially in people who are:

over the age of 30
taking SSRIs or tricyclics

Hypomania or mania

Antidepressants may trigger hypomania or mania in some people. This may stop if you stop taking the antidepressant, but sometimes it is interpreted as a sign of bipolar disorder. In this case, you may be given a new diagnosis and different medication.

Neuroleptic malignant syndrome

This is a rare, but serious, condition. It is usually associated with antipsychotic drugs (sometimes known as neuroleptics), but can occasionally occur with antidepressants.

The symptoms include:

changes in your level of consciousness
fast heart rate
high temperature
pale skin
stiffness
sweating
unstable blood pressure
urinary incontinence

Serotonin syndrome

This is a serious condition which, although rare, can be fatal. It can occur with any antidepressant, but is more likely with an SSRI – especially if you take it alongside other antidepressants, including MAOIs, and lithium (a mood stabiliser).

The symptoms are (most common first):

headaches
nausea (feeling sick)
diarrhoea
high temperature, shivering and sweating
high blood pressure and a fast heart rate
tremors, muscle twitching and over-responsive reflexes
convulsions (fits)
agitation, confusion and hallucinations
coma (loss of consciousness)

These symptoms may come on very suddenly.

Sexual problems

Certain sexual problems are a potential negative side effect of all SSRI and SNRI antidepressants. These include:

In women:

delayed orgasm or inability to reach orgasm
spontaneous orgasm

In men:

reduced sexual desire
failed erection, delayed ejaculation and lack of orgasm
priapism (prolonged erection) – this requires urgent medical attention, so if you experience this side effect, you should go to A&E or get a same-day appointment with your GP

Sometimes these side effects persist after you've come off the drug, and might continue indefinitely. If you experience this, you might want to report it on a Yellow Card.

SIADH (Syndrome of Inappropriate Antidiuretic Hormone Secretion)

SIADH is a rare side effect of some antidepressants – mainly tricyclics, SSRIs and SNRIs.

The antidiuretic hormone (vasopressin) is one of the hormones that control the production of urine. SIADH makes your body secrete too much antidiuretic hormone, which causes your body to hold on to water and makes you become low in sodium (this condition is called hyponatraemia).

This can lead to:

confusion
convulsions (fits)
hallucinations
coma (loss of consciousness), potentially leading to death
memory problems, difficulty concentrating, drowsiness and falls (mainly in older people)

Suicidal feelings

There is a possibility that taking an antidepressant could make you feel suicidal – even if you didn’t experience suicidal feelings before. This side effect is mainly associated with SSRI antidepressants, although all antidepressants carry this risk.

How could an antidepressant cause suicidal feelings?

There are two possible explanations:

When you’re severely depressed, your energy and motivation levels are very low, but taking an antidepressant can change this. A common theory for explaining suicide in the early stages of treatment is that the drug might give you the energy to act on suicidal urges before your depression has really started to lift.
A number of scientists believe that some drugs might directly cause suicidal thoughts and urges. The discussion usually focuses on SSRIs in particular, but research suggests that all antidepressants carry similar risks.

If you find you are experiencing suicidal feelings while taking antidepressants you should discuss it with doctor as soon as possible.

For more information about suicidal feelings, including information about what kind of support is available, see our pages on how to cope suicidal feelings.

If you feel in immediate crisis you can contact the Samaritans on 116 123 (freephone), or go to your local hospital's A&E department.

Tooth decay

Any drugs which cause a dry mouth can also cause tooth decay if you take them for a long time. This side effect is most commonly associated with tricyclic antidepressants.