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Antidepressant medicines explained

There are medicine and non-medicine treatments that can help with symptoms of depression, but no single treatment is right for everybody. It’s important to find a treatment that works for you, and this may take some trial and error. Find out more about the medicines available to treat moderate to severe depression. 

8 min read

How do antidepressant medicines work?

The decision to take an antidepressant, undertake psychological therapy, or combine both approaches, is very individual. Talk to your healthcare professional about what you think will work best for you.

Individual antidepressants can be grouped into different classes or groups, according to how they work chemically in the body. Within each group, there are usually several medicines that work in a similar way but may differ slightly from each other.

The different groups of antidepressants are about as effective as each other overall, but some people will respond to one antidepressant better than another. The type and severity of side effects can also be quite different between these groups of antidepressants. 

Serotonin is one of the neurotransmitters (brain chemicals) that transmit signals between cells in your brain. Serotonin, along with other neurotransmitters such as noradrenaline and dopamine, are thought to have an important effect on your mood. Different neurotransmitters control different functions — often more than one. The role of neurotransmitters in causing depression is not fully understood.

Antidepressants increase the amount of certain neurotransmitters, and this is how they are thought to reduce the symptoms of depression.

How effective are antidepressants?

About 50% of people who take an antidepressant find their depression symptoms are halved. 

Antidepressants are more effective for reducing symptoms in people with moderate or severe depression, rather than mild depression. Psychological therapies, such as CBT, are more effective than antidepressants for mild depression, and about equally effective for moderate depression, although the effects of CBT may last longer.

In clinical trials studying the effects of antidepressants, some people who took a placebo (an inactive, or sugar, pill) also felt better – about 30% of the placebo group found their symptoms were halved.

Placebos can have an effect because of the expectation of getting better, and because of other factors such as talking to the staff running the clinical trial. It may also be that some people improve over time anyway, regardless of treatment. This could be the case particularly with trials that recruited people with mild depression.

References

  1. Australian Medicines Handbook. Adelaide: Australian Medicines Handbook, 2017. [AMH Online] (accessed 20 January 2017).
  2. National Collaborating Centre for Mental Health. Surveillance review of CG90: Depression in adults: management and treatment (update) London: National Institute for Health and Clinical Excellence, 2013. [Online] (accessed 20 January 2017).
  3. Psychotropic Expert Group. Therapeutic Guidelines: Depression in adults. Published June 2013. Amended February 2015. © Therapeutic Guidelines Ltd (eTG Online) (accessed 20 January 2017).
  4. Williams JW Jr, Mulrow CD, Chiquette E, et al. A systematic review of newer pharmacotherapies for depression in adults: evidence report summary. Ann Intern Med 2000;132:743–56. [PubMed] (accessed 20 January 2017).

Which antidepressant?

If you and your healthcare provider agree a medicine may be helpful, there are a number of factors that need to be considered when deciding which antidepressant may be best. When tested in clinical trials, different antidepressants were all about as effective as each other. However, individuals can have very different responses to one antidepressant compared with another — so it can be a case of trial and error to find one that works best for you.

Other factors your healthcare provider will take into account when prescribing an antidepressant include possible side effects, any other illnesses you have, your age, and other medicines you take (some medicines can interact with each other). Being pregnant or breastfeeding are other important factors that also need to be taken into account.

For more information, see the Consumer Medicine Information (CMI) for your brand of medicine, available on our Medicine Finder page or from your pharmacist or prescribing physician.

Types of antidepressants

Antidepressants can be grouped according to how they work. The different types are:

  • SSRIs: selective serotonin reuptake inhibitors: citalopram, escitalopram, fluoxetine, fluvoxamine, paroxetine, sertraline
  • SNRIs: serotonin and noradrenaline reuptake inhibitors: duloxetine, venlafaxine, desvenlafaxine
  • Noradrenaline reuptake inhibitors: reboxetine
  • TCAs (tricyclic antidepressants):  amitriptyline, nortriptyline, clomipramine, dothiepin, doxepin, imiprimine, trimipramine*
  • RIMAs (reversible inhibitors of monoamine oxidase A): moclobemide
  • Tetracyclic antidepressants: mianserin
  • Tetracyclic analogues of mianserin (sometimes called noradrenergic and specific serotonergic antidepressant [NaSSA]): mirtazapine
  • MAOIs (monoamine oxidase inhibitors): phenelzine, tranylcypromine
  • Melatonergic antidepressants: agomelatine*

* not available on the PBS.

The different types of antidepressants are about as effective as each other, but the type and severity of side effects can be quite different between the types, and between individual medicines of the same type.

Antidepressant medicine side effects  

Like all medicines, antidepressants can have side effects, so if you are considering them as a treatment option, talk to your prescribing clinician about which side effects are more important for you to avoid. 

Keep in mind that your own experience of side effects with a particular antidepressant may differ from that seen in clinical trials, and from other people’s experiences.

Some side effects are short-term

Some side effects of antidepressants might go away after a few weeks of taking them. This usually applies to insomnia (sleep problems), nausea (sickness in the stomach) and dizziness. Others, such as sexual side effects, are not likely to go away if you are affected by them.

Some people feel nauseated when they first start an antidepressant — taking it with food might help if you get this side effect. This nausea usually goes away after a few weeks.

If you are having trouble with side effects from your antidepressant, talk to your prescriber or pharmacist about how to manage them. A different antidepressant might give you less troublesome side effects.

For more tips on coping with antidepressant side effects, see Antidepressants: Get tips to cope with side effects on the Mayo Clinic website.

Antidepressant Difference in side effects
Duloxetine Higher rates of stopping due to side effects than with SSRIs
Mirtazapine More weight gain than with SSRIs
Paroxetine Highest rate of discontinuation symptoms (equal to venlafaxine)
Highest rate of sexual dysfunction
Sertraline Highest rate of diarrhoea among the SSRIs
Venlafaxine More nausea and vomiting than with SSRIs
Highest rate of discontinuation symptoms (equal to paroxetine)
Higher rates of stopping due to side effects than with SSRIs

References

  1. Australian Medicines Handbook. Adelaide: Australian Medicines Handbook, 2017. [AMH Online] (accessed 20 January 2017).
  2. Bostwick JM. A generalist's guide to treating patients with depression with an emphasis on using side effects to tailor antidepressant therapy. Mayo Clin Proc 2010;85:538–50. [PubMed]
  3. Psychotropic Expert Group. Therapeutic Guidelines: Depression in adults. February 2015. Therapeutic Guidelines Ltd [eTG Online] (accessed 20 January 2017).
  4. Taylor D, Paton C, Kapur S. The Maudsley Prescribing Guidelines, 10th edn. London: Informa Healthcare, 2009.

Antidepressants and suicide risk

Concerns have been raised about an increased risk of suicidal thoughts and acts when people first start taking antidepressants. The concern has mainly been about selective serotonin reuptake inhibitors (SSRIs).

Suicidal thoughts and acts are a common symptom of depression, and often someone is at their lowest point when they first start taking an antidepressant. It can also take a few weeks for an antidepressant to work. This makes it difficult to assess whether people who think about suicide when they first start taking an antidepressant do so because of the medicine or the depression.

Although this is a difficult issue to give a definitive answer about, analysis of a large number of studies shows that there may be a small increase in suicidal thinking or behaviour in children, adolescents and young adults when they first start taking an antidepressant. The age-cut off for this increased risk seems to be about 25 years.

In adults aged 25–64 years, antidepressants seem to have no effect on suicidal behaviour but may reduce suicidal thoughts. In adults aged 65 years and over, antidepressants seems to reduce the risk of both suicidal thoughts and suicidal behaviour.

One possible explanation is that antidepressants increase a person’s energy before they begin to improve mood. This could make a depressed person more capable of acting on suicidal thoughts before the medicine improves their mood.

Antidepressants have only a small role in treating children, and they should be used only under the supervision of a child psychiatrist. Antidepressants should only be prescribed for adolescents by doctors with training in this area, who are very familiar with the side effects, and are able to provide close monitoring for suicidal thinking, particularly in the first four weeks.

If you have any suicidal thoughts, get help straight away. It’s a good idea to write down an advance action plan with your healthcare professional, for example, a list of five phone numbers to call; this allows some back-up in case you can’t get through to the first people you call.

If you are caring for someone starting treatment with an SSRI medicine, keep a close eye on them for worsening symptoms in the first few weeks, and call their healthcare professional if you are worried.

References

  1. Cheung K, Aarts N, Noordam R, et al. Antidepressant use and the risk of suicide: a population-based cohort study. J Affect Disord 2015; 174: 479-84. doi: 10.1016/j.jad.2014.12.032
  2. Erlangsen A, Yeates C. Age-Related Response to Redeemed Antidepressants Measured by Completed Suicide in Older Adults: A Nationwide Cohort Study. Am J Geriat Psych 2014: 10.1016/j.jagp.2012.08.008.
  3. McDermott B, Baigent M, Chanen A, et al; beyondblue Expert Working Committee. Clinical practice guidelines: depression in adolescents and young adults. Melbourne: beyondblue, 2010. [Online] (accessed 18 January 2017).
  4. Psychiatric Drug Safety Expert Advisory Panel. Report of the Psychiatric Drug Safety Expert Advisory Panel. Canberra: Therapeutic Goods Administration, 2009. [Online] (accessed 18 January 2017).
  5. Stone M, Laughren T, Jones ML, et al. Risk of suicidality in clinical trials of antidepressants in adults: analysis of proprietary data submitted to US Food and Drug Administration. BMJ 2009;339:b2880. [Online] (accessed 7 March 2012).

Antidepressants and sexual side effects

You may get sexual side effects from your antidepressant, such as losing your sex drive, having difficulty reaching orgasm, or (for men) problems getting a strong erection.

It’s important to talk to your prescribing physician if you get sexual side effects, as these can be difficult to deal with and may not go away if you are affected by them. Your healthcare provider may be able to suggest a treatment option for you, for example:

  • Trying a different antidepressant – some antidepressants have a lower risk of causing sexual side effects than others, or
  • Reducing the dose of your antidepressant

If other strategies haven’t worked, taking an erectile dysfunction medicine may be an option for some men.

Keep in mind that it can be difficult to tell whether antidepressants are the cause of your sexual problems, because depression itself can also be a cause.

References

  1. Australian Medicines Handbook. Adelaide: Australian Medicines Handbook, 2017. [AMH Online] (accessed 20 January 2017).
  2. Bostwick JM. A generalist's guide to treating patients with depression with an emphasis on using side effects to tailor antidepressant therapy. Mayo Clin Proc 2010;85:538–50. [PubMed].
  3. Psychotropic Expert Group. Therapeutic Guidelines: Depression in adults. February 2015. Therapeutic Guidelines Ltd [eTG Online] (accessed 20 January 2017).
  4. Taylor D, Paton C, Kapur S. The Maudsley Prescribing Guidelines, 10th edn. London: Informa Healthcare, 2009.

How long will I need to take antidepressants?

Often you will start to feel better within 2 to 4 weeks of starting an antidepressant, but it can take 6 to 8 weeks to feel the full effect. In general, you should see your healthcare provider at regular intervals to review your progress and discuss any issues related to treatment.

If you are not improving, your healthcare professional may discuss increasing your dose, switching to another antidepressant or referring you to another specialist.

If you are feeling better with antidepressant treatment you will usually need to keep taking it for 6 to 12 months to reduce the risk of your depression coming back. Having psychological therapy at the same time can further reduce the risk of your depression coming back. Some people may need to keep taking an antidepressant for a long time to prevent their symptoms coming back.

Stopping an antidepressant

If you and your healthcare provider have decided it’s time to stop taking your antidepressant, you will usually need to reduce the dose gradually to avoid symptoms such as nausea, dizziness and feeling jittery (discontinuation symptoms). How slowly you need to reduce the dose can depend on several factors, including the type of antidepressant, and how long you have been taking it.

In some cases you need to slowly reduce the dose before you change to another antidepressant too.

Ask your prescriber or pharmacist for advice on the best dose reduction plan for you.

References

  1. Australian Medicines Handbook. Adelaide: Australian Medicines Handbook, 2017. [AMH Online] (accessed 20 January 2017).
  2. National Collaborating Centre for Mental Health. Surveillance review of CG90: Depression in adults: management and treatment (update) London: National Institute for Health and Clinical Excellence, 2013. [Online] (accessed 20 January 2017).
  3. Psychotropic Expert Group. Therapeutic Guidelines: Depression in adults. February 2015. Therapeutic Guidelines Ltd [eTG Online] (accessed 20 January 2017).
  4. Royal Australian and New Zealand College of Psychiatrists, Coping with depression: Australian treatment guide for consumers and carers. 2009. (accessed 20 January 2017).

Complementary medicines and antidepressants

There are many complementary medicines and alternative therapies for depression. Some have been tested in scientific clinical trials, but many have not. The Therapeutic Goods Administration (TGA) does not assess complementary medicines to check that they work.

It’s important to be open with your doctor about any complementary medicines you take, because some can interact with your other medicines.

See the following websites for information about complementary medicines and alternative therapies for depression:

8 min read