The short answer
Most antidepressants start to help within 2 to 4 weeks, and many people notice small changes in the first week or two. The full effect for depression usually takes 6 to 8 weeks, and for anxiety disorders it can take up to 12 weeks. If you've noticed little or no change after a few weeks, keep taking the medicine and talk to your GP about whether to adjust the plan. Don't stop suddenly, because that can cause withdrawal symptoms.
On this page
How long do antidepressants take to work?
For depression, improvement may start 2 to 4 weeks after you begin an antidepressant, and the full effect can take 6 to 8 weeks [1]. Beyond Blue puts it this way: they take at least 2 weeks to start helping, and symptoms are likely to improve after 4 to 6 weeks [2].
Here's a rough guide to what to expect. Everyone is different, so treat it as a guide, not a deadline.
| Time since starting | What often happens |
|---|---|
| Week 1 to 2 | Side effects are often more noticeable early on; some people see small early improvements [3][4] |
| Week 2 to 4 | Improvement often starts to show [1] |
| Week 6 to 8 | Full effect for depression is usually reached [1] |
| Up to week 12 | Full effect for anxiety disorders may take this long [1][5] |
| 6 months and beyond | Maintenance treatment to prevent relapse after you've recovered [6] |
What happens in the first two weeks?
The old idea that antidepressants do nothing for a month isn't quite right. A meta-analysis of 28 trials with 5,872 people found that people taking an SSRI were already doing better than those on placebo by the end of the first week [3]. Improvement then continued, at a slowing rate, for at least 6 weeks [3].
Those early changes can be a useful sign. In a meta-analysis of 41 trials, mostly comparing mirtazapine with other treatments, improving by at least 20% within the first 2 weeks predicted later response with high sensitivity [7]. People who hadn't improved by that much by 2 weeks had little chance of a stable response on that treatment [7].
A later review of 17 trials and 14,779 patients found that 62% of people on an antidepressant were early improvers, compared with 47% on placebo [8]. Early improvers were about 8 times more likely to go on to respond [8].
What this means for you: if nothing at all has shifted after a couple of weeks, it's a good time to check in with your GP. It doesn't mean the medicine has failed, and it doesn't mean you should stop.
What might improve first?
Changes are often gradual, building over several weeks [3]. It can help to keep brief notes on your sleep, energy and mood each week to share at your review, so you and your GP can see the trend.
How long do antidepressants take to work for anxiety?
Anxiety tends to respond more slowly. Australian guidelines say it can take up to 6 weeks to feel a benefit from an antidepressant for anxiety, and up to 12 weeks for the full benefit [5]. healthdirect gives a similar timeline of 4 to 6 weeks for improvement and up to 12 weeks for the full effect [1].
The medicine needs to be taken every day, not just on anxious days [5]. Our guide to anxiety medication in Australia covers the options in more detail.
What if your antidepressant isn't working?
Some people don't respond to antidepressants, however long they take them, and their doctor then discusses other options [1]. Not responding to one medicine doesn't mean nothing will help.
Australian guidelines define a partial response as less than a 50% reduction in symptoms, and note that response is sometimes delayed [6]. Switching medicines is most useful when there's been no response or only minimal improvement, under about 20% [6]. Other options include increasing the dose, adding another medicine, or adding psychological therapy if you're not already having it [6].
Before changing medicines, your GP will usually check a few things with you:
- whether you've been taking it every day as prescribed
- whether the dose has been adequate for long enough
- whether alcohol or other drugs might be getting in the way (see antidepressants and alcohol)
- whether anything else, like a physical health problem or ongoing stress, is driving symptoms
If several treatments haven't helped, read our guide to treatment-resistant depression.
How long do side effects last?
Several common side effects are temporary and may fade within a few weeks of starting, but others can persist or appear later [4]. Common ones include headaches, dizziness, nausea, restlessness, sleep changes and sexual problems [1]. Tell your GP about any that bother you, because there are often ways to manage them [2].
Three things need prompt attention:
- Worsening mood or suicidal thoughts. Antidepressant product information in Australia warns about worsening depression and emerging suicidal thoughts, and advises close monitoring [9]. healthdirect notes this is a particular concern for children and young people when starting [1].
- Serotonin toxicity. This is rare, but symptoms such as tremor, confusion, sweating, fever or diarrhoea need urgent medical help [1].
- Unusually high mood or energy. In people with bipolar disorder, an antidepressant can sometimes trigger a manic or hypomanic episode [6]. Signs include unusually high mood or energy and needing much less sleep than usual without feeling tired [6]. Tell your GP promptly, and let them know if you or a close family member has had bipolar disorder.
How long should you keep taking antidepressants?
Feeling better is a reason to keep going, not to stop. A review of 31 trials found that continuing antidepressants after responding to treatment cut the odds of relapse by 70% [10]. On average, 41% of people who switched to placebo relapsed, compared with 18% who stayed on their medicine [10].
Australian guidelines recommend maintenance treatment for at least 6 months, with a detailed review at 1 year [6]. They suggest stopping is usually considered after you've been well for around 9 months to a year, and that people with recurrent episodes ideally continue for more than a year [6].
A UK trial tested what happens when people who feel well stop. Among 478 primary care patients with a history of repeated depression or at least 2 years on treatment, 56% of those who stopped relapsed within a year, compared with 39% who continued [11].
Why shouldn't you stop antidepressants suddenly?
Stopping suddenly is likely to cause withdrawal symptoms, including nausea, dizziness, confusion, anxiety or agitation, sweating and sleep problems [1]. Symptoms typically start a few days after stopping [6].
How common is this? A 2024 meta-analysis of 79 studies found about 31% of people had at least one discontinuation symptom after stopping an antidepressant, compared with 17% after stopping placebo [12]. Severe symptoms affected about 3% [12]. The authors estimated the true medicine-related rate at around 15%, or one in six to seven people [12].
Desvenlafaxine, venlafaxine, imipramine and escitalopram were linked with more frequent symptoms, and imipramine, paroxetine, venlafaxine and desvenlafaxine with more severe ones [12]. Agomelatine isn't associated with them [6].
Australian guidelines recommend reducing gradually, generally in steps at least a week apart, and more slowly for people at higher risk [6]. If you get withdrawal symptoms despite tapering, your GP may suggest slowing down further [1].
When to see a GP
See your GP if:
- you've had little or no improvement after a few weeks
- side effects are hard to live with
- you're thinking about stopping or reducing your medicine
- your mood is getting worse
If you'd like to talk to a GP about how you've been feeling, you can request an appointment. Mental Health Clinic is for adults 18 and over and isn't an emergency service.
A consultation doesn't guarantee a prescription. Your GP decides what's clinically appropriate.
If you're in crisis or thinking about suicide, call Lifeline on 13 11 14 or 000 in an emergency.
This page is general information, not medical advice.
Common questions
Can antidepressants work in the first week?
Yes, for some people. A meta-analysis of SSRI trials found people taking an SSRI were already doing better than those on placebo by the end of the first week, with improvement continuing for at least 6 weeks [3]. Early changes are often small, so it's worth giving the medicine time.
What should I do if my antidepressant isn't working after 4 weeks?
Keep taking it and book a review with your GP. Australian guidelines describe options including increasing the dose, adding another treatment such as psychological therapy, or switching medicines [6]. Which one makes sense depends on how much you've improved and how you're tolerating it.
Why do I feel worse when I first start an antidepressant?
Early side effects such as nausea, headache, restlessness and sleep changes are common, and several tend to fade within a few weeks [1][4]. Some people, especially young people, have suicidal thoughts when starting an antidepressant [1]. If that happens, contact your GP straight away, or call Lifeline on 13 11 14 or 000 in an emergency.
How long do I need to stay on antidepressants?
References
- healthdirect Australia. Antidepressants (last reviewed April 2025). Accessed November 2026. healthdirect.gov.au/antidepressant-medicines
- Beyond Blue. Treatments for depression. Accessed November 2026. beyondblue.org.au/mental-health/depression/treatments-for-depression
- Taylor MJ, Freemantle N, Geddes JR, Bhagwagar Z. Early onset of selective serotonin reuptake inhibitor antidepressant action: systematic review and meta-analysis. Arch Gen Psychiatry. 2006;63(11):1217-1223. pubmed.ncbi.nlm.nih.gov/17088502
- Carvalho AF, Sharma MS, Brunoni AR, et al. The safety, tolerability and risks associated with the use of newer generation antidepressant drugs: a critical review of the literature. Psychother Psychosom. 2016;85(5):270-288. pubmed.ncbi.nlm.nih.gov/27508501
- Andrews G, Bell C, Boyce P, et al. Royal Australian and New Zealand College of Psychiatrists clinical practice guidelines for the treatment of panic disorder, social anxiety disorder and generalised anxiety disorder. Aust N Z J Psychiatry. 2018;52(12):1109-1172. ranzcp.org/getmedia/5456b019-e2dd-4d7a-91d3-ca0ca8b356e3/anxiety-disor
- Malhi GS, Bell E, Bassett D, et al. The 2020 Royal Australian and New Zealand College of Psychiatrists clinical practice guidelines for mood disorders. Aust N Z J Psychiatry. 2021;55(1):7-117. doi.org/10.1177/0004867420979353
- Szegedi A, Jansen WT, van Willigenburg AP, et al. Early improvement in the first 2 weeks as a predictor of treatment outcome in patients with major depressive disorder: a meta-analysis including 6562 patients. J Clin Psychiatry. 2009;70(3):344-353. pubmed.ncbi.nlm.nih.gov/19254516
- Wagner S, Engel A, Engelmann J, et al. Early improvement as a resilience signal predicting later remission to antidepressant treatment in patients with major depressive disorder: systematic review and meta-analysis. J Psychiatr Res. 2017;94:96-106. pubmed.ncbi.nlm.nih.gov/28697423
- Therapeutic Goods Administration. Antidepressant utilisation and risk of suicide in young people. Accessed November 2026. tga.gov.au/safety/safety-monitoring-and-information/safety-alerts/anti
- Geddes JR, Carney SM, Davies C, et al. Relapse prevention with antidepressant drug treatment in depressive disorders: a systematic review. Lancet. 2003;361(9358):653-661. pubmed.ncbi.nlm.nih.gov/12606176
- Lewis G, Marston L, Duffy L, et al. Maintenance or discontinuation of antidepressants in primary care. N Engl J Med. 2021;385(14):1257-1267. pubmed.ncbi.nlm.nih.gov/34587384
- Henssler J, Schmidt Y, Schmidt U, et al. Incidence of antidepressant discontinuation symptoms: a systematic review and meta-analysis. Lancet Psychiatry. 2024;11(7):526-535. pubmed.ncbi.nlm.nih.gov/38851198
Published by Mental Health Clinic. Last updated 6 November 2026. This page is general information only and isn’t a substitute for advice about your own situation. If you or someone else is in danger, call 000.