How long do antidepressants take to work?
The published answer, and then the part nobody writes about: weeks two to six, where the cost has arrived and the benefit has not.
The published answer, first, because you came here for it: antidepressants “usually take 1 to 2 weeks to start having an effect and can take up to 8 weeks to work fully.”1 That is the NHS, and it is worth using their numbers rather than the ones that circulate — “four to six weeks” gets repeated a lot and sets an expectation that leaves people feeling overdue at week five.
So: something may shift early. The full picture takes considerably longer. Both halves matter.
Now the part almost nobody writes about, which is what actually happens in between.
Weeks two to six are the hard part, and they are meant to be
There is a stretch in the middle where the arithmetic is genuinely against you. Side effects, if you are going to get them, have usually arrived. The benefit, if it is coming, largely has not. You are paying the full cost of the decision and collecting none of the return.
That is not a sign the medication is wrong. It is the shape of the thing — cost front-loaded, benefit back-loaded. But it feels exactly like evidence of failure, which is why it is the point at which a lot of people quietly stop, without telling anyone, and conclude that antidepressants did not work for them.
If you are in that stretch right now, the single most useful thing to know is that it is the expected middle, not the outcome.
What helps while you are in it
Lower the bar for what counts as a day going well. During this window, “got through it” is a complete result. Measuring against how you would like to feel guarantees a daily verdict of failure, on a timescale where no verdict is available yet.
Watch what you did, not how you felt. Behaviour leaves a trace that mood does not — this is the whole argument in is my antidepressant working?, and it matters most here, because this is the stretch where your own read is least reliable.
Put the review date in the calendar now. “Come back if it does not improve” works far better with an actual date attached. It also gives the hard weeks a visible edge, which makes them easier to be inside.
Tell one person you are in it. Not for advice. So that the stretch is witnessed by somebody other than you at 11pm.
Write a line down every few days. In eight weeks you will want to know what week three was actually like, and you will not remember. A note on your phone is enough; Nagi's check-ins put it on a chart if you would rather not think about it.
The thing not to do alone
This window is exactly when unilateral stopping happens, and it is the one move to route through your prescriber rather than decide at night. The NHS guidance is flat: “Do not stop taking an antidepressant suddenly or without talking to your doctor first.”1
There is a specific trap here worth naming. Stopping abruptly can produce withdrawal effects that begin within days and last for weeks — and they can feel close enough to your depression returning to be mistaken for it. People conclude “see, I need it after all” or “see, I am back to square one,” when what they are actually experiencing is the stopping, not the underlying condition. That is a genuinely confusing position to be in, and entirely avoidable by making the decision with a plan.
Telling your prescriber that the middle stretch is hard is not a complaint and not a failure. If side effects are hard to manage, that is explicitly what they want to hear about1 — there are usually options, and none of them require you to have endured it silently first.
The short version
One to two weeks for something to start; up to eight for the full picture. The middle is the hard bit and it is expected, not diagnostic. Lower the bar, keep a light record, book the review, and take any decision about stopping to the person who prescribed it — particularly the decision that feels most obvious at midnight.
— Richard MacLean
Next: is my antidepressant working? — how to read the answer once the eight weeks are up.
Sources
- NHS, Overview — Antidepressants. nhs.uk — accessed 10 August 2026.
Nagi is a mental health companion, not a medical device, and nothing here is medical advice. Never start, stop, or change the dose of a prescribed medication without talking to your prescriber.