Starting an antidepressant: what the first eight weeks actually feel like

The most common reason people stop is that nobody told them what normal looks like.

For high-performing professionals in Chicago and Chicagoland: This article reflects clinical evidence and direct experience. If you're in the Chicago area or Illinois, contact me to discuss your concerns.

A large share of people who stop an antidepressant do so in the first few weeks, and the reason is usually not that the medication failed. It is that the experience did not match what they expected, and nobody had described the actual shape of it beforehand.

Here is that shape.

Week one to two: side effects arrive before benefit

This is the part that surprises people. The unpleasant effects of an SSRI — nausea, headache, disturbed sleep, a jittery restlessness, sometimes a blunted or slightly detached feeling — typically appear within days. The therapeutic effect does not.

So the first fortnight is often a period of feeling somewhat worse in exchange for nothing yet. Understanding that this is expected, rather than evidence the drug is wrong, is most of what gets people through it.

Most of these early effects diminish substantially by the end of week two. Nausea in particular tends to settle quickly, and taking the dose with food helps.

Week two to four: the first signals

Improvement rarely arrives as a lifting of mood. More often the earliest changes are in sleep, appetite, and energy — the physical substrate — while the subjective sense of feeling better lags behind.

People frequently notice this in retrospect rather than in the moment. A partner comments that you seem more like yourself. You realise you have not been lying awake at 3am for a week. The mood itself may still feel flat.

This asymmetry — function improving before feeling improves — is normal, and worth watching for deliberately.

Week four to eight: an adequate trial

The National Institute of Mental Health notes that antidepressants generally take four to eight weeks to produce their full effect, and that sleep, appetite, and concentration commonly improve before mood does.

This is why changing medication at week three is usually premature. An adequate trial means an adequate dose for an adequate duration. Abandoning at three weeks answers nothing — you learn only that it had not worked yet.

What warrants an earlier conversation

Some things should not wait for the eight-week mark:

• Any increase in thoughts of self-harm or suicide, particularly in the first weeks and particularly in younger adults
• A marked increase in energy or activity combined with reduced need for sleep, which can indicate a bipolar spectrum condition the medication has unmasked
• Severe agitation or restlessness that does not settle
• Rash, fever, or unusual bruising

These are reasons to contact your prescriber promptly rather than to endure.

What determines whether it works

Response to any single antidepressant is meaningfully less than certain. A substantial minority of people do not respond adequately to the first medication tried, and that is an expected clinical outcome rather than a failure on anyone's part.

What improves the odds is an accurate diagnosis to begin with, an adequate dose rather than a cautious one held indefinitely, and a clinician who reviews at intervals short enough to catch a non-response early.

The practical version

Expect side effects before benefit. Expect the first four weeks to be uninformative. Take it at the same time daily, with food if it unsettles your stomach, and keep a rough note of sleep and appetite rather than trying to rate your mood day to day, which is unreliable.

And tell your prescriber what is actually happening rather than what you think they want to hear. The whole exercise depends on accurate reporting.

Published August 2026 · Reviewed for accuracy against the sources listed above.