Depression: the facts about antidepressants

Lesley Dobson

There are several different kinds of anti-depressant medications which work in different ways.



If you have moderate to severe depression, or mild depression that has gone on for a long time, your GP may prescribe antidepressants. They’re thought to work by boosting the activity of chemicals in our brains, known as neurotransmitters, which send signals from cell to cell.

If you are over 65, you’ll find that your GP will adjust your prescription to take your age into account. This will usually be half the standard dose prescribed for most antidepressants.

Serotonin reuptake inhibitors (SSRIs)

These are the newest type of anti-depressants, (and the subjects of the report on antidepressants LINK), and the ones that are usually prescribed first. They stop a chemical in the brain, serotonin, (a neurotransmitter) being absorbed back into the cells that released it, so allowing it to work for longer. Low serotonin levels are thought to be a factor in depression.

However, these antidepressants do have side effects, including anxiety, trouble sleeping, restlessness, nausea, headaches and reduced sex drive. Most people only have a few of these side effects, and they may go away as your body becomes used to the drug, but, generally, as we get older, we can become more prone to side effects.

SSRIs include Fluoxetine (Prozac) and Paroxetene (Seroxat).

Tricyclic Antidepressants (TCAs)

TCAs work by raising the levels of neurotransmitters serotonin and noradrenaline. However TCAs tend to have more side effects such as a dry mouth and constipation and can make you drowsy and reduce your blood pressure, making you more prone to falls.

Your GP will usually prescribe SSRIs before considering TCAs. If you are taking TCAs, it’s dangerous to take more than your prescribed dose. And you shouldn’t take them if you’ve recently had a heart attack or are at risk of irregular heart beat (serious cardiac arrhythmias).

TCAs include amitriptyline, imipramine and nortriptyline.

Monoamine Oxidase Inhibitors (MAOIs)

These antidepressants also affect the levels of serotonin and noradrenaline in the brain, stopping them from being broken down. MAOIs are normally only prescribed if SSRIs and TCAs have failed to work, and aren’t really suitable for older people.

MAOIs include phenelzine, and isocarboxacid.

Serotonin-Norepinephrine Reuptake Inhibitors (SSNIs)

These are quite a new type of antidepressant, which have a similar effect to TCAs. However they can cause side effects, including an increase in blood pressure, so may not be suitable for everyone.

SSNIs include venlafaxine, nefazodone and mirtazapine.

Severe depression

There are a number of treatments that are only prescribed for people with severe depression. These include:

  • Lithium carbonate and lithium citrate. You'll normally only be prescribed this medication if other antidepressants haven't worked for you. You need to take it alongside your existing treatment, and would need to have regular blood tests to check that your lithium levels aren't too high.
  • Electro convulsive therapy (ECT): This is normally only used if no other treatments have worked, and is not used often. It's given in hospital, under a general anaesthetic, when a small electric current is passed through your brain. A course of treatment usually lasts from six to 12 sessions.



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