The First Two Weeks on an Antidepressant

The commonest reason antidepressant treatment fails is not that the drug was wrong. It is that the person stopped taking it during the second week.

That is an entirely understandable thing to do. Nobody warned them that the first fortnight often feels worse rather than better, so when it did, the obvious conclusion was that the tablets did not suit them.

This is what actually happens, and why.

Why it can feel worse first

Most antidepressants prescribed in general practice are SSRIs, which raise available serotonin in the brain. The level rises within days. The clinical benefit takes considerably longer — typically four to six weeks — because the improvement depends on slower downstream changes in how receptors respond, not on the serotonin level itself.

The side effects, unfortunately, follow the fast timeline. So there is a period of one to two weeks where you have all the side effects and none of the benefit. That gap is the hardest part of the treatment and it is entirely predictable.

What is common in the first fortnight

• Increased anxiety, restlessness or agitation — the most disconcerting one, because it is the opposite of what you were expecting
• Nausea, which is very common and usually settles within one to two weeks
• Headache
• Disturbed sleep, or vivid and strange dreams
• Drowsiness or, less often, insomnia
• Loose stools

Almost all of this settles. The nausea and headache typically go within a fortnight. The early anxiety usually eases within one to two weeks and often responds to starting at a lower dose.

What the timeline actually looks like

• Week 1–2. Side effects at their most noticeable. Little or no benefit. This is the phase people abandon
• Week 2–4. Side effects easing. The first changes are often not in mood at all — sleep improves, appetite returns, or you find you can get things done. Other people frequently notice before you do
• Week 4–6. Mood improvement becomes apparent
• Week 6–12. Full effect. This is the point at which to judge whether the drug is working, not before

If there is no change at all by four weeks at an adequate dose, that is a reason to review the dose or the drug — which is a different conversation from stopping.

When to seek help urgently

Contact a doctor the same day — or call 999 or go to A&E if you are in immediate danger — if you experience:

• New or worsening thoughts of harming yourself
• Marked agitation or a feeling of being unable to keep still, which can be a specific side effect called akathisia and needs reviewing, not enduring
• A significant worsening of mood rather than the mild early unsettledness described above
• Confusion, a high temperature, shivering, muscle twitching, sweating or a racing heart — which can indicate serotonin syndrome, particularly if you take other medicines affecting serotonin
• Any allergic reaction

This matters most in under-25s. There is a recognised, small increase in suicidal thoughts in younger people during the early weeks of treatment, which is why anyone under 25 starting an antidepressant should be reviewed within the first week or two rather than left to get on with it.

If you need help now and cannot wait: call 111 and choose the mental health option, or the Samaritans on 116 123, free, at any hour.

Things worth knowing before you start

Start low. Beginning at half the usual dose for the first week reduces early side effects considerably, particularly in anyone prone to anxiety. It costs a week and saves a great many people from stopping.

Take it at a consistent time. If it makes you drowsy, take it at night; if it disturbs sleep, take it in the morning. There is no universally right answer — it depends on the drug and on you.

Antidepressants are not addictive, but stopping suddenly causes discontinuation symptoms. These are two different things, and the distinction gets lost. Discontinuation — dizziness, electric-shock sensations, flu-like feelings, irritability — is why they must be tapered rather than stopped abruptly, and it is not evidence of dependence.

Plan for six months at least. Current guidance is to continue for at least six months after you feel well, because stopping as soon as you improve is strongly associated with relapse.

Medication is not the whole treatment. Talking therapy works, works well in combination, and is available free on the NHS by self-referral without going through a GP at all. Where that is the better route we will say so.

What to ask for

If you are being started on an antidepressant, it is entirely reasonable to ask: what should the first fortnight feel like, when should I expect to notice a change, when are you reviewing me, and what do I do if I feel worse rather than better?

A ten-minute appointment rarely has room for all of that. It is one of the clearest arguments for twenty.

See our anxiety and depression treatment page, or book a mental wellness consultation. If you are already under a mental health team, changes should go through them — we will support rather than work around your existing care.