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What are antidepressants?

Antidepressants are a type of medication commonly used for the treatment of depression. They have to be prescribed by a doctor.

Some people with mild depression often benefit from exercise, self-help groups, and online CBT, and will not require antidepressants. For those with mild to moderate depression a talking treatment such as counselling or CBT might be recommended. If someone has moderate to severe depression your doctor might recommend antidepressants in combination with talking therapies such as cognitive behavioural therapy (CBT).

How do antidepressants work?

Antidepressants gradually increase the levels of some chemicals in the brain called neurotransmitters that can improve mood and emotion. Serotonin and noradenaline (norepinephrine) are examples of neurotransmitters.

While clinical studies have shown than antidepressants are effective, it is not clear if they address the underlying cause of depression or its mechanisms. Most people with depression will experience an improvement in their symptoms after 2 to 4 weeks of taking the medication. It takes about 4 to 6 weeks for the antidepressants to work so you should continue taking your medication as prescribed unless you experience major side effects, in which case you should not stop taking the medication before seeking your doctor's advice. Some people will improve while on the first antidepressant prescribed, others might have to try two or more until their symptoms improve. Most people will need to take the antidepressant for at least 4 to 6 months after they have shown an improvement.

Antidepressants could be prescribed for longer periods of time, for example, 5 years or more, in cases of previous episodes of depression. Antidepressants are not addictive.

Antidepressants work more slowly in elderly people who might have to take them for at least 6 weeks before they see any signs of improvement.

If you have been on antidepressants for 6 weeks without missing a dose and have not experienced an improvement in your symptoms, you should discuss other treatments with your doctor.

Types of antidepressants

There are about 30 different types of antidepressants available and the most commonly used include:

  • Selective serotonin reuptake inhibitors (SSRIs) such as paroxetine, fluoxetine and citalopram. These are antidepressants that block the reuptake of serotonin only so that serotonin levels in the brain are increased. SSRIs are effective and have fewer side effects than older antidepressants and are commonly prescribed for moderate to severe depression. Children under the age of 18 can be prescribed fluoxetine by a specialist. Studies have found a link between the risk of self-harm and suicidal behaviour in children under 18 years of age and some SSRIs.
  • Serotonin-norepinephrine reuptake inhibitors (SNRIs) block the reuptake of serotonin and norepinephrine (noradrenaline). They include new antidepressants such as venlafaxine duloxetine and mirtazapine. They may be more effective than SSRIs but can cause a rise in blood pressure and so are less often prescribed.
  • Tricyclic antidepressants (TCAs) such as imipramine and amitriptyline are older types of antidepressants that are usually prescribed for moderate to severe depression when SSRIs or SNRIs have not been effective. They have more side effects than newer antidepressants such as SSRIs or SNRIs.
  • Monoamine oxidase inhibitors (MAOIs) such as moclobemide and phenelzine have been used for the treatment of moderate to severe depression for longer than SSRIs or SNRIs. They block the effects of monoamine oxidase, an enzyme that metabolises serotonin, adrenaline (epinephrine) and dopamine. If you are taking MAOIs you should avoid food and drinks containing a protein called tyramine, for example, red wine, aged cheese, as they interact with the MAOI resulting in high blood pressure.
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