Antidepressants are a group of medicines used to treat moderate to severe depression.
If you need help or want to talk to somebody about your mental health, you can get support from any of the following:
- Free call or text 1737 any time for support from a trained counsellor
- Lifeline 0800 543 354 (0800 LIFELINE) or free text 4357 (HELP)
- Suicide Crisis Helpline 0508 828 865 (0508 TAUTOKO)
- Healthline 0800 611 116
- Samaritans 0800 726 666.
On this page, you can find the following information:
- What are antidepressants?
- What to consider when choosing an antidepressant?
- Can I use herbal supplements when taking antidepressants?
- How do antidepressants work?
- How long will I need to take antidepressants for?
- Don't stop taking your antidepressant medicine suddenly
- What to know about the side effects of antidepressants
Antidepressants are medicines used to treat mainly moderate to severe depression. They can help improve mood and increase motivation for people who may have lost interest in activities they once enjoyed. They can also help with sleep, thinking and concentration. Antidepressants work best when they are used together with psychological therapies, like CBT (cognitive behavioural therapy) and lifestyle changes. Read more about treating depression.
Antidepressants are not usually needed, and often not very effective for mild depression. CBT, talking therapy and regular exercise work better for mild depression.
Antidepressants are also used to treat other conditions such as generalised anxiety disorder (GAD), eating disorders, obsessive-compulsive disorder and post-traumatic stress disorder. They are also sometimes used to treat people with long-term (chronic) pain.
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There are many types of antidepressants. Different medicines suit different people. The choice of antidepressant medicine will depend on:
- the severity and type of your illness
- whether you have other medical conditions
- other medicines you might be taking
- your response to antidepressant medicines in the past
- possible side effects.
Antidepressants available in Aotearoa New Zealand
Selective serotonin reuptake inhibitors (SSRIs)
Serotonin and noradrenaline reuptake inhibitors (SNRIs)
Tricyclic antidepressants (TCAs)
Some people find that herbal products like St John's Wort can be useful for depression but it can interact with antidepressant medicines and other medicines. Before taking herbal supplements, ask your doctor or pharmacist if they interact with the medicine you are taking.
We don't know for certain, but researchers think that antidepressants work by increasing the activity of certain chemicals working in our brains called neurotransmitters. Certain neurotransmitters, such as serotonin and noradrenaline, are linked to mood and emotion.
While depression is not simply a deficiency of these chemicals, we do know that antidepressant medications help to relieve symptoms of depression and anxiety in approximately 50–70% of people who try them. Some people will respond to one antidepressant better than another so changes may be needed to find the best type and dose of medicine for you.
Neurotransmitters may also affect pain signals sent by nerves, which may explain why some antidepressants can help relieve long-term pain.
Antidepressant medicines work best if you take them every day. When you first start taking an antidepressant medicine, you won’t feel better straight away. Most people start to feel better after taking them for 2 to 4 weeks. However, it can take up to 6 to 8 weeks for them to really work.
How long you need to take antidepressants for will depend on a number of factors and is best discussed with your doctor. Most people will need to take these medicines for at least 6 to 12 months. If you stop taking it too early, your signs of depression or anxiety may come back. During the first few months of treatment, you'll usually see your doctor or a specialist nurse at least once every few weeks to see how well the medicine is working.
If you think your antidepressant medicine isn't working for you, don't stop taking it suddenly. Talk to your doctor about the right time to stop taking your medicine. When you’re ready, your doctor will work out a plan with you. They will slowly lower the amount you take over a few weeks until you’re not taking it at all. This lowers the chance of problems as you stop taking it, eg, feeling dizzy, tired or worried or having trouble sleeping.
Like all medicines antidepressants can cause side effects but not everyone gets them. Different antidepressants have different side effects. Most side effects are mild and go away after a few weeks as your body gets used to the medicine such as trouble sleeping (insomnia), feeling like you might throw up (nausea) and feeling dizzy.
At the start of treatment some people can experience side effects such as agitation and anxiety in the first few weeks. Keep in mind that things will get better and these side effects are likely to pass as your body gets used to the new medicine. Talk to your healthcare provider about what you can do if side effects are a problem. They may suggest taking a smaller dose (amount) or trying a different medicine.
If you suspect you, or someone you know, might be suffering from depression, read more from our depression section or visit thelowdown.co.nz or depression.org.nz for helpful information, including a self-test.
The following links provide further information on antidepressants. Be aware websites from other countries may contain information that differs from Aotearoa New Zealand recommendations.
Antidepressants Royal College of Psychiatrists, UK
Antidepressants Patient Info, UK
Antidepressants – selecting one that's right for you Mayo Clinic, US
Depression – treatment options Option Grid
- The role of medicines in the management of depression in primary care BPAC, NZ, 2021
- Antidepressant drugs NZ Formulary