Starting an Antidepressant: What the First 8 Weeks Look Like

If you’re a week or two into a new antidepressant and feel worse instead of better, you’re in the stretch where many people quit. In one U.S. study, 42.4% of adults who started an antidepressant for depression stopped within the first 30 days. Only 27.6% were still taking it after three months.

Your body tends to register side effects before your mood registers relief. In one SSRI study of 401 people starting treatment, 86% reported at least one side effect, and most side effects first appeared within two weeks. Knowing which changes come first, and which ones matter, gives the waiting period real precision.

The standard advice is to give the medication six to eight weeks before judging it. That advice rests on solid evidence. In STAR*D, one of the largest real-world antidepressant studies, people who improved on their first medication usually needed more than a month to respond, as the data below show. The results are real, and the timeline is well documented.

But waiting eight weeks without measuring anything is no longer the best version of that advice, and at Siggy we’d rather you know what to look for at week two than find out at week eight.

Current guidelines add an early checkpoint: a measurable drop in symptoms within the first two to four weeks that predicts how the rest of the trial is likely to go. This guide walks through each stage with that checkpoint in mind. The timeline below comes from trial data rather than reassurance, so what you’re watching for is the evidence.

What This Page Covers

• Why Do Antidepressants Take Weeks to Work?
• What Happens in the First Two Weeks?
• What Is the Week 4 Checkpoint?
• When Do Most People Start Feeling Better?
• Do Antidepressant Side Effects Go Away?
• What Happens After Week 8?
• When Should You Call Your Prescriber?
• Start Your First Weeks With a Plan

Why Do Antidepressants Take Weeks to Work?

The idea that nothing happens for weeks is only partly true. A 2006 meta-analysis of SSRI trials pooling 28 studies and 5,872 people found that SSRIs beat placebo by the end of the first week. People on an SSRI were also more likely to see their depression scores cut in half by week one.

What takes weeks is the size of the change. In the same analysis, improvement kept building at a slower rate for at least six weeks. So the first weeks usually feel like small shifts in sleep, energy, or how heavy the mornings are, well before you’d describe yourself as better.

Here’s how the first eight weeks typically unfold, based on the studies and guidelines cited throughout this guide.

Weeks	What the Research Shows	What to Do
1 to 2	Most side effects begin; small gains possible	Report side effects before stopping; urgent care if severe
2 to 4	Early improvement window (20% or more)	Review progress with your prescriber
5 to 6	Average time to response in STAR*D	Keep taking it as prescribed
7 to 8	Average time to remission in STAR*D	Decide to continue, adjust, or switch

What Happens in the First Two Weeks?

This is usually the hardest stretch. Side effects tend to show up before you feel much benefit, and that gap can make stopping feel like the logical choice. If you’re struggling, tell your prescriber before deciding to quit, since changes to timing or dose may be possible.

There’s also a safety point worth knowing. An FDA analysis of 372 trials with about 99,000 adults found that the risk of suicidal thoughts or behavior on antidepressants depended strongly on age. The risk was higher than placebo for adults under 25, neutral to possibly protective from 25 to 64, and lower than placebo at 65 and older. If you notice new or worsening thoughts of suicide, contact your prescriber right away or call or text 988.

Our guide to Zoloft side effects in the first two weeks covers what’s typical for one of the most common SSRIs.

What Is the Week 4 Checkpoint?

The CANMAT 2023 guidelines define early improvement as a 20% or greater drop on a symptom scale within two to four weeks of starting. Response means a 50% drop. Remission means scoring in the healthy range, such as 4 or less on the PHQ-9 questionnaire, which our PHQ-9 explainer walks through.

That early checkpoint is useful because it predicts what comes next. A 2009 meta-analysis of 41 trials with 6,562 patients found that early improvement within two weeks identified at least 81% of people who went on to a stable response. Without any early improvement, the chance of a stable response later was low. The trials studied mirtazapine and comparison antidepressants, so the exact numbers may differ by drug.

The guideline’s practical takeaway is straightforward. If you see no early improvement by week four, it’s time to discuss raising the dose or switching, rather than waiting another month. Our post on signs your dose may be too low can help you prepare for that conversation.

When Do Most People Start Feeling Better?

For people who do improve on their first medication, most of the change arrives between weeks five and eight. In a STAR*D analysis of 2,876 outpatients taking citalopram for up to 14 weeks, people who responded took about 5.5 weeks on average to get there. Those who reached remission took about 6.2 to 6.9 weeks.

The same analysis is honest about the odds. Only about 27% to 33% of people reached remission on that first medication, depending on the scale used. Not getting there on the first try is common, and it usually means the next step is an adjustment rather than the end of the road. Our guide on what to do if your antidepressant isn’t working at 8 weeks lays out those options.

Do Antidepressant Side Effects Go Away?

Some do, and some don’t, which is something many guides gloss over. In the study of 401 people starting SSRIs, most side effects began in the first two weeks, but most people were still having the same side effects when interviewed about three months later. That included 83% of people with sexual side effects.

The same study found that prescribing physicians underestimated how often side effects happened and how much they bothered patients. That’s a strong argument for speaking up early and specifically. “I’m having trouble with sexual side effects” gives your prescriber something to act on, and options exist. Our patient strategies for SSRI sexual side effects are a good place to start.

What Happens After Week 8?

Feeling better at week eight usually means the medication is working, not that you’re finished with it. A Lancet review of 31 trials with 4,410 people found that continuing an antidepressant after responding cut the odds of relapse by 70%. The average relapse rate was 41% for people switched to placebo and 18% for people who stayed on treatment.

The CANMAT 2023 guidelines now recommend continuing for six to twelve months after remission, and longer for people with risk factors for recurrence. When it is time to stop, taper with your prescriber. A 2024 meta-analysis of 79 studies found that 31% of people stopping an antidepressant had at least one discontinuation symptom, compared with 17% of people stopping a placebo. Severe symptoms affected about 2.8%.

When Should You Call Your Prescriber?

Don’t wait for your next scheduled visit if any of these happen:

• New or worsening thoughts of suicide or self-harm
• A sudden surge of energy, racing thoughts, or little need for sleep
• A rash, swelling, or trouble breathing
• Side effects that make it hard to keep taking the medication
• No noticeable improvement at all by week four

For anything that feels like an emergency, call 911. This article is for education only and isn’t a substitute for personal medical advice. It reflects sources available as of October 2026.

Start Your First Weeks With a Plan

A lot of people describe the first month the same way: “No one checks in to see if it’s actually working.” You deserve a clear picture of what to expect, a checkpoint to measure against, and a prescriber who knows your history before anything is prescribed. Start your anonymous intake with Siggy to share your symptoms, sleep, and medication history in your own words, without giving your name or email. It’s free, and you’ll get a downloadable summary you can bring to any clinician. If an antidepressant is part of the right plan, a licensed prescriber reviews your full clinical picture first. For more on reading the early signs, see our guide on how to know if your antidepressant is working.