Find a psychiatrist

Antidepressant medication

What are antidepressants?

Antidepressants are medications that can reduce symptoms of depression, such as feelings of sadness, thoughts of suicide, tiredness, poor appetite and sleep problems.

They are used to treat moderate and severe depression.

Antidepressants are also used to treat anxiety disorders, obsessive compulsive disorder (OCD) and post-traumatic stress disorder (PTSD).

What types are there?

There are several different types of medications for treating depression.

Newer antidepressant medications work by altering the amounts of natural chemicals in your brain, such as serotonin or noradrenaline.

These types of medications include:

  • ‘selective serotonin reuptake inhibitors’ (SSRIs), such as citalopram, escitalopram, fluoxetine, fluvoxamine, paroxetine and sertraline
  • other medications that alter serotonin, such as vortioxetine
  • medications that alter both serotonin and noradrenaline, such as desvenlafaxine, duloxetine, mianserin, mirtazapine and venlafaxine
  • medications that alter serotonin and melatonin, such as agomelatine.

Older types of medication are used when the newer medications don’t work or are not appropriate. These types of medications include:

  • ‘tricyclic antidepressants’, such as amitriptyline, clomipramine, dothiepin, doxepin, imipramine and nortriptyline
  • ‘monoamine oxidase inhibitors’, such as moclobemide, phenelzine and tranylcypromine.

St John’s wort (a herbal medicine) is sometimes used for mild depression, but it can cause problems with other medications. St John’s wort should not be used at the same time as a prescription antidepressant medication. If you are thinking of using any non-prescription medications to treat your depression, talk to your doctor first.

What should I know if I’ve been prescribed an antidepressant?

  • Take every dose of your medication at the time recommended to you by your doctor.
  • When starting a medication, give it time to start working properly.
  • Don’t change your medication without talking your doctor.
  • If you have symptoms that you think could be the side effects of medications, tell your doctor as soon as possible.

What are the side effects?

Antidepressant medications can sometimes cause side effects, especially when you start a new medication.

Side effects of antidepressants differ between medications and from person to person.

Ask your doctor or pharmacist to explain the possible side effects of your medication. You can ask for a printed leaflet, or read about the medication at:

If you have side effects that bother you, speak to your doctor about them. They might be able to reduce the side effects by changing the dose or switching to a different medication. Some side effects will get better after a few days and some can be treated with other medications.

Possible side effects can include:

  • weight gain
  • sexual problems (e.g. taking longer to reach orgasm)
  • sleepiness or tiredness
  • sleep problems
  • dizziness
  • agitation
  • dry mouth
  • diarrhoea or constipation
  • nausea
  • headache
  • teeth-grinding
  • problems with the heart and blood pressure
  • seizures. 

Sometimes young people have suicidal thoughts while they're taking antidepressant medication. Children, teenagers and young adults need to be checked during the first few weeks of treatment to make sure they are safe.

Many people only have side effects in the first few days or weeks.

How long will I need to take an antidepressant?

Antidepressants need time to start working. Most people improve within a few weeks, but you may need to take an antidepressant medication for up to 6 weeks before your symptoms of depression are under control.

After you start to get better, you usually need to keep taking the medication for at least 6 months. This helps you recover completely, and can stop the symptoms coming back.

Most people don’t need to stay on antidepressant medications for years, but it may be necessary if you've had depression before.

Taking medication every day

Many people find it hard to keep taking their medication.

If you have trouble remembering to take your medication, or you are taking several different medications, ask your pharmacist to package the tablets in containers with compartments for each day. They might use a blister pack (sometimes called a Webster-Pak or Medico Pak) or a plastic container (called a dosette box).

It is a good idea to always go to the same pharmacy so they can keep track of all your medications and give advice about them when needed.

What if the medication doesn’t work for me?

If an antidepressant medication is right for you, your symptoms will start to improve within about 2 weeks. If you are no better after 3–6 weeks, your doctor might recommend a different medication.

Pregnancy and breastfeeding

If you are pregnant, planning to become pregnant or breastfeeding it's essential to discuss this with your doctor.

It’s best to be cautious about using medications during pregnancy. Some medications could harm an unborn baby, but stopping medication during pregnancy may be risky for the mother. 

If you are already pregnant, talk to your doctor as soon as possible about keeping yourself and your baby safe during pregnancy and breastfeeding.

If you need medication for postnatal depression, talk to your doctor about whether it’s safe to breastfeed. 

Other medications

Before you start taking a new medication, tell your doctor if you are taking any other medication (including over-the-counter or complementary medicines). Some medications cannot be mixed.

More about medications for mental illness


  • Antidepressants reduce symptoms of depression such as feelings of sadness, thoughts of suicide, tiredness, poor appetite and sleep problems.
  • Antidepressants can take about 2 weeks to start working.
  • Some people need to take antidepressants long-term to keep their symptoms under control.
  • If you are prescribed an antidepressant, talk to your doctor about the benefits and risks for you.
Page last reviewed Feb 2017 | C1014V1

This is a general guide only, and does not replace individual medical advice. Please speak to your doctor for advice about your situation. The RANZCP is not liable for any consequences arising from relying on this information. Subject matter experts, people with lived experience of mental illness and carers all contributed to this fact sheet.